Methods for Implanting a Valve Prothesis

ABSTRACT

A method for implanting a valve prosthesis at a native cardiac valve complex of a subject comprises implanting a distal fixation member of the valve prosthesis downstream of a native valve of the native valve complex such that two or more engagement arms of the distal fixation member apply, to a downstream side of the native valve, a first axial force directed upstream. The method also comprises implanting a proximal fixation member of the valve prosthesis at least partially upstream of the native valve, such that the proximal fixation member applies, to an upstream side of the native valve, a second axial force directed downstream, such that application of the first and second forces couples the valve prosthesis to the native valve complex. The engagement arms and the proximal fixation member capture leaflets of the native valve therebetween without folding over leaflets of the native valve.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication 60/845,728, filed Sep. 19, 2006, entitled, “Fixation memberfor valve,” which is assigned to the assignee of the present applicationand is incorporated herein by reference.

The present application is related to the following US patentapplications, all of which were filed on even date herewith, areassigned to the assignee of the present application, and areincorporated herein by reference, which applications are entitled:

-   -   “Sinus-engaging valve fixation member”;    -   “Valve fixation member having engagement arms”;    -   “Valve prosthesis implantation techniques”;    -   “Axial-force fixation member for valve”; and    -   “Leaflet-sensitive valve fixation member.”

FIELD OF THE INVENTION

The present invention relates generally to prosthetic devices for thetreatment of body lumens, and specifically to a valve prosthesis forsuch body lumens.

BACKGROUND OF THE INVENTION

PCT Publication WO 05/002466 to Schwammenthal et al., which is assignedto the assignee of the present application and is incorporated herein byreference, describes prosthetic devices for treating aortic stenosis.

PCT Publication WO 06/070372 to Schwammenthal et al., which is assignedto the assignee of the present application and is incorporated herein byreference, describes a prosthetic device having a single flow fieldtherethrough, adapted for implantation in a subject, and shaped so as todefine a fluid inlet and a diverging section, distal to the fluid inlet.

US Patent Application Publication 2006/0149360 to Schwammenthal et al.,which is assigned to the assignee of the present application and isincorporated herein by reference, describes a prosthetic deviceincluding a valve-orifice attachment member attachable to a valve in ablood vessel and including a fluid inlet, and a diverging member thatextends from the fluid inlet, the diverging member including a proximalend near the fluid inlet and a distal end distanced from the proximalend. A distal portion of the diverging member has a largercross-sectional area for fluid flow therethrough than a proximal portionthereof.

U.S. Pat. No. 6,730,118 to Spencer et al., which is incorporated hereinby reference, describes a valve prosthesis device suitable forimplantation in body ducts. The device comprises a support stent, whichcomprises a deployable construction adapted to be initially crimped in anarrow configuration suitable for catheterization through the body ductto a target location, and adapted to be deployed by exertingsubstantially radial forces from within by means of a deployment deviceto a deployed state in the target location; and a valve assemblycomprising a flexible conduit having an inlet end and an outlet, made ofpliant material attached to the support beams providing collapsibleslack portions of the conduit at the outlet. The support stent isprovided with a plurality of longitudinally rigid support beams of fixedlength. When flow is allowed to pass through the valve prosthesis devicefrom the inlet to the outlet, the valve assembly is kept in an openposition, whereas a reverse flow is prevented as the collapsible slackportions of the valve assembly collapse inwardly providing blockage tothe reverse flow.

U.S. Pat. No. 7,018,406 to Seguin et al., which is incorporated hereinby reference, describes a prosthetic valve assembly for use in replacinga deficient native valve, comprising a replacement valve supported on anexpandable valve support. If desired, one or more anchors may be used.The valve support, which entirely supports the valve annulus, valveleaflets, and valve commissure points, is configured to be collapsiblefor transluminal delivery and expandable to contact the anatomicalannulus of the native valve when the assembly is properly positioned.The anchor engages the lumen wall when expanded and prevents substantialmigration of the valve assembly when positioned in place. The prostheticvalve assembly is compressible about a catheter, and restrained fromexpanding by an outer sheath. The catheter may be inserted inside alumen within the body, such as the femoral artery, and delivered to adesired location, such as the heart. When the outer sheath is retracted,the prosthetic valve assembly expands to an expanded position such thatthe valve and valve support expand within the deficient native valve,and the anchor engages the lumen wall.

U.S. Pat. No. 7,018,408 to Bailey et al., which is incorporated hereinby reference, describes prosthetic cardiac and venous valves and asingle catheter device, and minimally invasive techniques forpercutaneous and transluminal valvuloplasty and prosthetic valveimplantation. The device consists generally of a stent body member, agraft, and valve flaps. The graft is preferably a biocompatible,fatigue-resistant, membrane which is capable of endothelialization, andis attached to the stent body member on at least portions of either orboth the lumenal and ablumenal surfaces of the stent body member bysuturing to or encapsulating stent struts. The valve leaflets arepreferably formed by sections of the graft material attached to thestent body member. The stent body member is shaped to include thefollowing stent sections: proximal and distal anchors, a intermediateannular stent section, and at least one valve arm or blood flowregulator struts.

U.S. Pat. No. 6,458,153 and US Patent Application Publication2003/0023300 to Bailey et al., which are incorporated herein byreference, describe prosthetic cardiac and venous valves and a singlecatheter device, and minimally invasive techniques for percutaneous andtransluminal valvuloplasty and prosthetic valve implantation.

US Patent Application Publication 2004/0186563 Lobbi, which isincorporated herein by reference, describes a prosthetic heart valvehaving an internal support frame with a continuous, undulating leafletframe defined therein. The leaflet frame has three cusp regionspositioned at an inflow end intermediate three commissure regionspositioned at an outflow end thereof. The leaflet frame may be clothcovered and flexible leaflets attached thereto form occluding surfacesof the valve. The support frame further includes three cusp positionersrigidly fixed with respect to the leaflet frame and located at theoutflow end of the support frame intermediate each pair of adjacentcommissure regions. The valve is desirably compressible so as to bedelivered in a minimally invasive manner through a catheter to the siteof implantation. Upon expulsion from catheter, the valve expands intocontact with the surrounding native valve annulus and is anchored inplace without the use of sutures. In the aortic valve position, the cusppositioners angle outward into contact with the sinus cavities, andcompress the native leaflets if they are not excised, or the aortic wallif they are. The support frame may be formed from a flat sheet ofnitinol that is bent into a three-dimensional configuration and heatset. A holder having spring-like arms connected to inflow projections ofthe valve may be used to deliver, reposition and re-collapse the valve,if necessary.

US Patent Application Publication 2003/0130729 to Paniagua et al., whichis incorporated herein by reference, describes a percutaneouslyimplantable replacement 10 heart valve device and a method of makingsame. The replacement heart valve device comprises a stent member madeof stainless steel or self-expanding nitinol, and a biological tissueartificial valve means disposed within the inner space of the stentmember. An implantation and delivery system has a central part whichconsists of a flexible hollow tube catheter that allows a metallic wireguide to be advanced inside it. The endovascular stented-valve is aglutaraldehyde fixed bovine pericardium which has two or three cuspsthat open distally to permit unidirectional blood flow.

US Patent Application Publication 2004/0236411 to Sarac et al., which isincorporated herein by reference, describes a prosthetic valve forreplacing a cardiac valve, including an expandable support member and atleast two valve leaflets made of a first layer of biological materialselected from peritoneal tissue, pleural tissue, or pericardial tissue.A second layer of biological material is attached to the support member.The second layer is also made from peritoneal tissue, pleural tissue, orpericardial tissue. The second layer includes a radially inwardly facingsurface that defines a conduit for directing blood flow. The valveleaflets extend across the conduit to permit unidirectional flow ofblood through the conduit.

US Patent Application Publication 2005/0075720 to Nguyen et al., whichis incorporated herein by reference, describes a method and system forminimally invasive replacement of a valve. The system includes acollapsible valve and anchoring structure, devices and methods forexpanding the valve anchoring structure, adhesive means to seal thevalve to the surrounding tissue, a catheter-based valve sizing anddelivery system, native valve removal means, and a temporary valve andfilter assembly to facilitate removal of debris material. The valveassembly comprises a valve and anchoring structure for the valve,dimensioned to fit substantially within the valve sinus.

US Patent Application Publication 2006/0058872 to Salahieh et al., whichis incorporated herein by reference, describes an apparatus forendovascularly replacing a patient's heart valve. In some embodiments,the apparatus includes an expandable anchor supporting a replacementvalve, the anchor and replacement valve being adapted for percutaneousdelivery and deployment to replace the patient's heart valve, the anchorhaving a braid having atraumatic grasping elements adapted to grasptissue in a vicinity of the patient's heart valve.

US Patent Application Publication 2005/0137688 Salahieh et al., which isincorporated herein by reference, describes a method for percutaneouslyreplacing a heart valve of a patient. In some embodiments the methodincludes the steps of percutaneously delivering a replacement valve andan expandable anchor to a vicinity of the heart valve in an unexpandedconfiguration; expanding the anchor to a deployed configuration in whichthe anchor contacts tissue at a first anchor site; repositioning theanchor to a second anchor site; and deploying the anchor at the secondanchor site.

US Patent Application Publication 2005/0137690 to Salahieh et al., whichis incorporated herein by reference, describes apparatus forendovascularly replacing a patient's heart valve, including: a deliverycatheter having a diameter of 21 french or less; an expandable anchordisposed within the delivery catheter; and a replacement valve disposedwithin the delivery catheter. The invention also includes a method forendovascularly replacing a heart valve of a patient. In some embodimentsthe method includes the steps of: inserting a catheter having a diameterno more than 21 french into the patient; endovascularly delivering areplacement valve and an expandable anchor to a vicinity of the heartvalve through the catheter; and deploying the anchor and the replacementvalve.

US Patent Application Publication 2005/0137691 to Salahieh et al., whichis incorporated herein by reference, describes apparatus forendovascularly replacing a patient's heart valve, including: acustom-designed anchor; and a replacement valve, wherein thecustom-designed anchor is adapted to engage native leaflets of the heartvalve, and wherein the anchor and the valve are adapted for in vivoexpansion and coupling to one another to form composite apparatus thatendovascularly replaces the heart valve. The invention also includes amethod for endovascularly replacing a patient's heart valve. In someembodiments the method includes the steps of: providing apparatuscomprising an anchor piece and a replacement valve piece; endovascularlydelivering the anchor piece to a vicinity of the heart valve in acollapsed delivery configuration; expanding the anchor piece to adeployed configuration; engaging at least one valve leaflet of the heartvalve with the anchor piece; endovascularly delivering the replacementvalve piece to the vicinity of the heart valve in a collapsed deliveryconfiguration; expanding the replacement valve piece to a deployedconfiguration; and coupling the valve piece to the anchor piece in vivoto form composite two-piece apparatus that endovascularly replaces thepatient's heart valve.

US Patent Application Publication 2005/0137695 to Salahieh et al., whichis incorporated herein by reference, describes apparatus forendovascularly replacing a patient's heart valve, including areplacement valve adapted to be delivered endovascularly to a vicinityof the heart valve; an expandable anchor adapted to be deliveredendovascularly to the vicinity of the heart valve; and a lock mechanismconfigured to maintain a minimum amount of anchor expansion.

US Patent Application Publication 2005/0143809 to Salahieh et al., whichis incorporated herein by reference, describes techniques forendovascularly replacing a heart valve of a patient. One aspectdescribed is a method including the steps of endovascularly delivering areplacement valve and an expandable anchor to a vicinity of the heartvalve in an unexpanded configuration; and applying an externalnon-hydraulically expanding or non-pneumatically expanding actuationforce on the anchor to change the shape of the anchor, such as byapplying proximally and/or distally directed force on the anchor using areleasable deployment tool to expand and contract the anchor or parts ofthe anchor. Another aspect described includes an apparatus including areplacement valve; an anchor; and a deployment tool comprising aplurality of anchor actuation elements adapted to apply anon-hydraulically expanding or non-pneumatically expanding actuationforce on the anchor to reshape the anchor.

US Patent Application Publication 2005/0182483 to Osborne et al., whichis incorporated herein by reference, describes a venous valve prosthesishaving a substantially non-expandable, valve portion comprising avalve-closing mechanism, such as a pair of opposing leaflets; and ananchoring portion, such as one or more self-expanding frames or stentsthat are expandable to anchor the prosthesis at the implantation site.In one embodiment, the rigid valve portion includes a deposition ofmaterial such as pyrolitic carbon to reduce the thrombogenicity of theblood-contacting surfaces. The anchoring portions preferably include acovering, such as a tubular construct of synthetic or collagen-derivedmaterial (such as a bioremodelable ECM material), which attaches aboutthe support structure such that blood flow is directed through the valvemechanism as it transitions from the larger diameter anchoring portionto the intermediate, smaller-diameter portion of the prosthesis. Inanother embodiment, the valve support housing and valve-closing elementsare delivered in a collapsed, folded, and/or dissembled state sized fordelivery, then manipulated in situ to the second expanded configuredfollowing deployment.

US Patent Application Publication 2005/0197695 to Stacchino et al.,which is incorporated herein by reference, describes a cardiac-valveprosthesis adapted for percutaneous implantation. The prosthesisincludes an armature adapted for deployment in a radially expandedimplantation position, the armature including a support portion and ananchor portion, which are substantially axially coextensive with respectto one another. A set of leaflets is coupled to the support portion. Theleaflets can be deployed with the armature in the implantation position.The leaflets define, in the implantation position, a flow duct that isselectably obstructable. The anchor portion can be deployed to enableanchorage of the cardiac-valve prosthesis at an implantation site.

US Patent Application Publication 2005/0240200 to Bergheim, which isincorporated herein by reference, describes methods and systems forintroducing a delivery device in the heart at or near the apex of theheart, wherein the methods include advancing the prosthesis to a targetsite, and disengaging the prosthesis from the delivery device at thetarget site for implantation. Specifically, the valve replacementsystems are described for delivering a replacement heart valve to atarget site in or near a heart. The valve replacement system comprises atrocar or other suitable device to penetrate the heart at or near theapex of the heart, a delivery member that is movably disposed within thetrocar, and a replacement cardiac valve disposed on the delivery member.The delivery member may further comprise mechanical or inflatableexpanding members to facilitate implantation of the prosthetic valve atthe target site.

US Patent Application Publication 2006/0025857 to Bergheim et al., whichis incorporated herein by reference, describes valve prostheses adaptedto be initially crimped in a narrow configuration suitable forcatheterization through body ducts to a target location, and adapted tobe deployed by exerting substantially radial forces from within by meansof a deployment device to a deployed state in the target location.

US Patent Application Publication 2006/0025855 to Lashinski et al.,which is incorporated herein by reference, describes a cardiovascularprosthetic valve comprising an inflatable body that has at least a firstinflatable chamber and a second inflatable chamber that is not in fluidcommunication with the first inflatable chamber. The inflatable body isconfigured to form, at least in part, a generally annular ring. A valveis coupled to the inflatable body. The valve is configured to permitflow in a first axial direction and to inhibit flow in a second axialdirection opposite to the first axial direction. A first inflation portis in communication with the first inflatable chamber. A secondinflation port in communication with the second inflatable chamber.

US Patent. Application Publication 2006/0047338 to Jenson et al., whichis incorporated herein by reference, describes a cardiac valve having asupport frame having a first end member and a second end member opposingthe first end member in a substantially fixed distance relationship, anda cover extending over the support frame to allow for unidirectionalflow of a liquid through the valve.

US Patent Application Publication 2006/0052867 to Revuelta et al., whichis incorporated herein by reference, describes a method for functionallyreplacing a previously implanted prosthetic heart valve. The methodincludes positioning a replacement prosthetic heart valve within aninternal region defined by the previously implanted prosthetic heartvalve. The replacement prosthetic heart valve is then physically dockedto the previously implanted prosthetic heart valve. With this technique,the previously implanted prosthetic heart valve serves as a platform forsecurement of the replacement prosthetic heart valve to the patient'snative tissue.

US Patent Application Publication 2006/0074485 to Realyvasquez, which isincorporated herein by reference, describes methods and apparatus forvalve repair or replacement. In one embodiment, the apparatus is a valvedelivery device comprising a first apparatus and a second apparatus. Thefirst apparatus includes a heart valve support having a proximal portionand a distal portion and a heart valve excisor slidably mounted on saidfirst apparatus. The second apparatus includes a fastener assemblyhaving a plurality of penetrating members mounted to extend outward whenthe assembly assumes an expanded configuration; and a heart valveprosthesis being releasably coupled to said second apparatus. The firstapparatus and second apparatus are sized and configured for delivery tothe heart through an opening formed in a femoral blood vessel. The heartvalve prosthesis support is movable along a longitudinal axis of thedevice to engage tissue disposed between the anvil and the valveprosthesis.

US Patent Application Publication 2006/0259136 to Nguyen et al., whichis incorporated herein by reference, describes a heart valve prosthesishaving a self-expanding multi-level frame that supports a valve bodycomprising a skirt and plurality of coapting leaflets. The frametransitions between a contracted delivery configuration that enablespercutaneous transluminal delivery, and an expanded deployedconfiguration having an asymmetric hourglass shape. The valve body skirtand leaflets are constructed so that the center of coaptation may beselected to reduce horizontal forces applied to the commissures of thevalve, and to efficiently distribute and transmit forces along theleaflets and to the frame. Alternatively, the valve body may be used asa surgically implantable replacement valve prosthesis.

U.S. Pat. No. 7,137,184 to Schreck, which is incorporated herein byreference, describes methods for forming a support frame for flexibleleaflet heart valves from a starting blank include converting atwo-dimensional starting blank into the three-dimensional support frame.The material may be superelastic, such as NITINOL, and the method mayinclude bending the 2-D blank into the 3-D form and shape setting it. Amerely elastic material such as ELGILOY may be used and plasticallydeformed in stages, possibly accompanied by annealing, to obtain the 3-Dshape.

U.S. Pat. No. 6,558,418 to Carpentier et al., which is incorporatedherein by reference, describes a highly flexible tissue-type heart valveis disclosed having a structural stent in a generally cylindricalconfiguration with cusps and commissures that are permitted to moveradially. The stent commissures are, constructed so that the cusps arepivotably or flexibly coupled together at the commissures to permitrelative movement therebetween. The stent may be cloth-covered and maybe a single element or may be made in three separate elements for athree cusp valve, each element having a cusp portion and two commissureportions; adjacent commissure portions for each pair of adjacent stentelement combining to form the stent commissures. If the stent hasseparate elements their commissure portions may be pivotably or flexiblecoupled, or may be designed to completely separate into independentleaflets at bioresorbable couples. The cloth covering may have anoutwardly projecting flap that mates, with valve leaflets (e.g.,pericardial leaflets) along the cusps and commissures. A connecting bandmay be provided that follows the cusps and commissures and extendsoutwardly. The valve is connected to the natural tissue along theundulating connecting band using conventional techniques, such assutures.

U.S. Pat. No. 6,296,662 to Caffey, which is incorporated herein byreference, describes heart valve prosthesis including a heart valveformed of a flexible material. An elongated stent member is provided inthe valve and includes terminal ends. A plurality of flexible postmembers are formed in the stent member. Each post member includes a pairof opposite sides. A crimp collar interconnects the terminal ends of thestent member. The crimp collar is positioned between adjacent postmembers. A first radius is formed in the stent member between the crimpcollar and an adjacent side of each adjacent post member. A plurality ofsecond radii are formed in the stent member between an opposite side ofa first one of the adjacent post members and an opposite side of asecond one of the adjacent post members. The second radii are greaterthan each first radius.

The following patents and patent application publication, all of whichare incorporated herein by reference, may be of interest:

-   U.S. Pat. No. 6,312,465 to Griffin et al.-   U.S. Pat. No. 5,908,451 to Yeo-   U.S. Pat. No. 5,344,442 to Deac-   U.S. Pat. No. 5,354,330 to Hanson-   US Patent Application Publication 2004/0260389 to Case et al.

SUMMARY OF THE INVENTION

In some embodiments of the present invention, an aortic valve prosthesisfor treating a native stenosed valve comprises two portions that areconfigured to axially sandwich a native valve complex from the aortic(i.e., downstream) and left-ventricular (i.e., upstream) sides thereof,and a collapsible valve that is configured to be open during systole andclosed during diastole. The two portions typically include a collapsibleinner support structure that serves as a proximal (i.e., upstream)fixation member, and a collapsible outer support structure that servesas a distal (i.e., downstream) fixation member. The distal fixationmember is configured to be positioned in an ascending aorta of thesubject, and to apply, to an aortic side of the native valve complex, afirst axial force directed toward a left ventricle of the subject. Theproximal fixation member is configured to be positioned at leastpartially on the left-ventricular side of the aortic valve, typicallyextending at least partially into the left ventricular outflow tract(LVOT), and to apply, to a left-ventricular side of the aortic annulus(typically, at the top of the left ventricle), a second axial forcedirected in a downstream direction (i.e., toward the ascending aorta).Application of the first and second forces couples the prosthesis to thenative valve.

In some embodiments of the present invention, the valve prosthesis isconfigured to treat a native pulmonary valve.

For some applications, the distal fixation member is shaped so as todefine engagement arms that are configured to be positioned distal tothe native annulus, at least partially within the aortic sinuses, and,for some applications, to apply the first axial force. Typically, forthese applications, the distal fixation member is configured to applythe first axial force to the floors of the aortic sinuses.

The valve prosthesis is configured to be placed in the native stenosedvalve using a minimally-invasive approach, such as an endovascular ortransapical approach. The valve prosthesis is configured to beself-expanding and easy to position, and typically does not requiresuturing to be held in place. The native valve leaflets typically do notneed to be opened to the maximal extent possible, but rather only to theextent which allows insertion of the narrowest part of the valveprosthesis, the diameter of which is typically about 15-20 mm. Placementof the valve prosthesis is thus accompanied by reduced risk of embolismof calcific or thrombotic material dislodged from the valve and coronaryocclusion compared to many conventional valve prosthesis implantationprocedures.

Unlike some valve prostheses known in the art, the valve prosthesis ofsortie embodiments of the present invention does not rely for fixationon high forces applied outwardly radially against the native valve.Typically, a ratio of (a) the first or second axial force applied by thevalve prosthesis to (b) the radial force applied outwardly by the valveprosthesis against the native valve is greater than 1.5:1, e.g., greaterthan 3:1 or greater than 6:1, For some applications, the valveprosthesis applies a radial force of less than 0.5 pounds (0.23kilogram-force) outwardly against the native valve, such as less than0.3 pounds (0.14 kgf), or less than 0.1 pounds (0.045 kgf). For someapplications, the valve prosthesis is configured to apply the firstaxial force with a force of at least 40 g during diastole, and thesecond axial force with a force of at least 1 g (e.g., at least 5 g)during systole. For some applications, the valve prosthesis isconfigured to apply the first axial force with a force of no more than1700 g during diastole.

In other embodiments, the valve prosthesis applies a force outwardlyradially against the native valve that is sufficient to aid withfixation of the prosthesis, or sufficient to fixate the prosthesis.

In some embodiments of the present invention, the valve prosthesisapplies such outwardly radial forces only to the extent necessary toallow insertion of the prosthesis through the native valve, but notsufficiently to fully open the native leaflets to the maximum extentpossible. This level of radial force application, typically inconjunction with the distal fixation member placed upon the aortic sideof the native valve leaflets, prevents pushing of the native valveleaflets against the coronary ostia. Additionally, the configuration ofthe valve prosthesis generally reduces or eliminates leakage around theprosthetic valve, by avoiding damage to the native leaflets. Such damageis avoided because the valve prosthesis typically does not fully open,fold over, or crimp the native leaflets. Instead, the valve prosthesisgently envelops the leaflets between the distal fixation member (e.g.,the engagement arms thereof) and the proximal fixation member. Suchdamage to the native leaflets is also avoided because the valveprosthesis typically does not apply substantial axial force to thenative valve commissures. Furthermore, for applications in which thevalve prosthesis comprises a bulging proximal skirt, as describedhereinbelow, the skirt generally helps reduce leakage around theprosthetic valve.

Typically, the valve prosthesis does not apply an axial force to thetips of native valve leaflets that would result in shortening of thelength of the leaflets, or forced bending, crimping, or folding over ofthe leaflets. Given the complex composition of the leaflets (fibroustissue, soft atheroma, and calcifications), such compression mightresult in the application of shear forces to the leaflets, which mightdislodge material and cause an embolism.

Although the valve prosthesis is generally described herein with respectto treating a native aortic valve, in some embodiments the valveprosthesis is used to treat a native pulmonary valve (i.e., the othersemilunar valve in the heart), or another native valve of the body, withappropriate modifications to the valve prosthesis.

As used herein, including in the claims, the “native valve complex”includes the native semilunar valve leaflets, the annulus of the valve,the subvalvular tissue on the ventricular side, and the lower half ofthe semilunar sinuses.

There is therefore provided, in accordance with an embodiment of thepresent invention, apparatus including a prosthesis for implantation ata native semilunar valve of a native valve complex of a subject, thenative valve complex having three semilunar sinuses and three nativecommissures, the prosthesis including a valve prosthesis support, whichincludes a support structure including exactly three engagement armsthat meet one another at three respective junctures,

wherein the engagement arms are shaped so as define three peak complexesat the three respective junctures, and three trough complexes, each ofwhich is between two of the peak complexes, and

wherein upon implantation of the prosthesis, each of the engagement armsis at least partially disposed within a respective one of the semilunarsinuses, such that each of the peak complexes is disposed distal to andin rotational alignment with a respective one of the native commissures,and each of the trough complexes is disposed at least partially withinthe respective one of the semilunar sinuses.

In an embodiment, the native semilunar valve includes a native aorticvalve of the subject, the semilunar sinuses include respective aorticsinuses, and upon implantation of the prosthesis, each of the engagementarms is disposed at least partially within the respective one of theaortic sinuses.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve of the subject, the semilunar sinuses include respective pulmonarysinuses, and upon implantation of the prosthesis, each of the engagementarms is disposed at least partially within the respective one of thepulmonary sinuses.

In an embodiment, the engagement arms are shaped such that each of thepeak complexes includes exactly one peak at its respective one of thejunctures. In an embodiment, the engagement arms are shaped such thateach of the trough complexes includes exactly one trough.

For some applications, the engagement arms are shaped so as to defineexactly one trough between each two of the peak complexes.Alternatively, the engagement arms are shaped so as to define aplurality of troughs between each two of the peak complexes.

In an embodiment, the engagement arms are configured to touch respectivetransitions between the respective semilunar sinuses and respectivenative leaflet roots of the native valve complex, upon implantation ofthe prosthesis.

In an embodiment, the prosthesis is configured such that, duringimplantation of the prosthesis, the peak complexes self-align with therespective native commissures.

For some applications, upon implantation of the prosthesis, each of thepeak complexes is disposed in the rotational alignment with therespective one of the native commissures with a rotational offset.Alternatively, upon implantation of the prosthesis, each of the peakcomplexes is disposed in the rotational alignment with the respectiveone of the native commissures without a rotational offset.

In an embodiment, the valve prosthesis support, upon implantation of theprosthesis, does not press upon the native commissures of the nativesemilunar valve. Alternatively, the peak complexes, upon implantation ofthe prosthesis, touch the respective native commissures of the nativesemilunar valve at the respective junctures of the engagement arms.

For some applications, the prosthesis is configured to apply a radialforce of less than 0.5 pounds outwardly against the native semilunarvalve.

In an embodiment, the prosthesis is configured such that any radialforce applied by the prosthesis outwardly against the native semilunarvalve is insufficient by itself to chronically maintain the prosthesisin position with respect to the native valve complex under conditions ofnormal cardiac motion.

In an embodiment, the prosthesis is configured, upon implantationthereof, to embrace, such as gently embrace, without squeezing, leafletsof the native semilunar valve.

For some applications, the prosthesis is configured, upon implantationthereof, such that the engagement arms apply a force to distal sides ofthe leaflets of the native semilunar valve while the engagement arms aregenerally parallel to the distal sides of the leaflets.

In an embodiment, the valve prosthesis support is configured such that,upon implantation of the prosthesis, the valve prosthesis support doesnot fold over leaflets of the native semilunar valve. In an embodiment,the valve prosthesis support is configured such that, upon implantationof the prosthesis, the valve prosthesis support does not push leafletsof the native semilunar valve towards respective semilunar sinus floorsof the native valve complex. In an embodiment, the prosthesis isconfigured to less than fully open leaflets of the native valve complexwhen the prosthesis is implanted at the native valve complex. In anembodiment, the valve prosthesis support is configured to elevateleaflets of the native semilunar valve front within the semilunarsinuses upon implantation of the prosthesis.

In an embodiment, the prosthesis is configured such that, uponimplantation at the native valve complex, the engagement arms arealigned by rotation with respective ones of the semilunar sinuses.

In an embodiment, each of the engagement arms includes at least oneextension element, that extends from the engagement arm, which at leastone extension element is configured to engage a sinus floor of therespective one of the semilunar sinuses upon implantation of theprosthesis.

In an embodiment, each of the engagement arms is configured to engage arespective one of the semilunar sinuses upon implantation of theprosthesis. For some applications, each of the engagement arms isconfigured to firmly engage the respective one of the semilunar sinusesupon implantation of the prosthesis.

In an embodiment, the valve prosthesis support is configured not toapply a force to leaflets of the native semilunar valve sufficient tohold the prosthesis in place.

For some applications, each of the engagement arms is shaped so as todefine at least one extension element that extends from the engagementarm, and each of the engagement arms and its respective at least oneextension element are configured such that the engagement arm engages,via the at least one extension element, a sinus floor of the respectiveone of the semilunar sinuses upon implantation of the prosthesis.

For some applications, each of the engagement arms is shaped to define alength, parallel to a longitudinal axis of the prosthesis, between (a)at least one of the junctures and (b) a contact point of one of theengagement arms that meets at the juncture with a sinus floor of therespective one of the semilunar sinuses upon implantation of theprosthesis, which length is greater than 6 mm.

In an embodiment, the prosthesis includes a prosthetic valve includingone or more prosthetic leaflets, at least a portion of each of theprosthetic leaflets is configured to assume a closed position duringdiastole and an open position during systole, and the at least a portionis not directly coupled to any of the engagement arms. For someapplications, the prosthetic valve is coupled to the support structuresuch that at least 50% of an axial length of the prosthetic leaflets isdistal to native valve leaflets of the native semilunar valve, uponimplantation of the prosthesis. For some applications, the prostheticvalve includes a collapsible pliant material, configured to assume theopen and closed positions. For some applications, the valve prosthesissupport and the prosthetic valve are configured to define a single flowfield through the valve prosthesis support and the prosthetic valve.Alternatively, the valve prosthesis support and the prosthetic valve areconfigured to define a plurality of flow fields through the valveprosthesis support and the prosthetic valve.

In an embodiment, the support structure includes exactly threecommissural posts, to which the junctures of the engagement arms arerespectively attached. For some applications, upon implantation of theprosthesis, the commissural posts are rotationally aligned withrespective ones of the native commissures.

In an embodiment, the engagement arms are shaped so as to flare outlaterally to an angle with respect to a central axis of the prosthesis.In an embodiment, the engagement arms conform to a shape of a semilunarroot of the native valve complex when the engagement arms are flaredout. In an embodiment, the engagement arms are shaped so as to curveoutwards laterally. In an embodiment, a shape of at least one of theengagement arms is generally characterized by a function z″(r)>=0, wherez is a height of any given point on the at least one engagement armmeasured along a longitudinal axis of the prosthesis, and r is adistance from the longitudinal axis to the given point. For someapplications, the shape is generally characterized by the functionz″(r)>0.

In an embodiment, the support structure is configured to serve as adistal fixation member, the valve prosthesis support includes a proximalfixation member, and the proximal fixation member and the engagementarms of the distal fixation member are configured to axially sandwichthe native valve complex from ventricular and downstream sides thereof,respectively, upon implantation of the prosthesis.

In an embodiment, the engagement arms are configured to be disposed,during an implantation procedure, at least partially within therespective ones of the semilunar sinuses before the proximal fixationmember is positioned at least partially on the ventricular side of thenative valve complex, such that the arms prevent leaflets of the nativevalve complex from opening more than a predetermined desired amount, theopening being because of force applied by the proximal fixation memberto the leaflets.

In an embodiment, the proximal fixation member is configured to bepositioned at least partially in a ventricle of the subject uponimplantation of the prosthesis.

In an embodiment, the proximal fixation member is shaped so as to defineat least one barb configured to apply a barb force to the ventricularside of the native valve complex. For some applications, the at leastone barb is configured to pierce the ventricular side of the nativevalve complex. Alternatively, the at least one barb is configured toprotrude into tissue of the ventricular side of the native valvecomplex, without piercing the tissue. In an embodiment, the distalfixation member is shaped so as to define at least one mating barb, andthe at least one barb of the proximal fixation member is configured toengage the at least one mating barb, so as to help hold the prosthesisin place.

In an embodiment, the proximal and distal fixation members arecollapsible. For some applications, the distal fixation member isconfigured to be positioned, during an implantation procedure, in adownstream artery while collapsed, and to be expanded before theproximal fixation member is positioned at least partially on theventricular side of the native valve complex, the downstream arteryselected from the group consisting of: an ascending aorta, and apulmonary trunk. For some applications, the apparatus includes at leastone tube selected from the group consisting of an overtube and a trocar,and the proximal and distal fixation members are configured to be storedin the selected tube while collapsed, and to expand upon being deployedfrom the selected tube.

In an embodiment, the proximal fixation member includes an inner supportstructure, and the distal fixation member includes an outer supportstructure that is placed partially over the inner support structure. Forsome applications, the inner and outer support structures are configuredto be coupled to one another during an implantation procedure.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which theengagement arms extend radially outward. In an embodiment, theprosthesis is configured such that, upon implantation at the nativevalve complex, the strut supports are aligned with the respective nativecommissures. In an embodiment, the inner support structure is shaped soas to define a plurality of distal diverging inner struts.

In an embodiment, the inner support structure is shaped so as to definea bulging proximal skirt, a proximal portion of which is configured toapply an axial force directed toward a downstream artery selected fromthe group consisting of: an ascending aorta, and a pulmonary trunk. Forsome applications, the prosthesis includes a graft covering that coversat least a portion of the skirt.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts, and the skirt extends fromthe inner struts.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which theengagement arms extend radially outward, and each of the strut supportsis positioned over a respective one of the inner struts.

In an embodiment, the engagement arms are positioned over a portion ofthe skirt.

In an embodiment, the prosthesis includes a valve including acollapsible pliant material, configured to assume a closed positionduring diastole and an open position during systole, and the pliantmaterial includes a plurality of segments, at least two of which arecoupled together by one of the strut supports and its respective one ofthe inner struts.

There is further provided, in accordance with an embodiment of thepresent invention, apparatus including a prosthesis for implantation ata native aortic valve of a native valve complex of a subject, the nativevalve complex having exactly two aortic sinuses and two nativecommissures, the prosthesis including a valve prosthesis support, whichincludes a support structure including exactly two engagement arms thatmeet one another at two respective junctures,

wherein the engagement arms are shaped so as define two peak complexesat the two respective junctures, and two trough complexes, each of whichis between the peak complexes, and

wherein upon implantation of the prosthesis, each of the engagement armsis at least partially disposed within a respective one of the aorticsinuses, such that each of the peak complexes is disposed distal to andin rotational alignment with a respective one of the native commissures,and each of the trough complexes is disposed at least partially withinthe respective one of the aortic sinuses.

In an embodiment, the engagement arms are shaped such that each of thepeak complexes includes exactly one peak at its respective one of thejunctures. In an embodiment, the engagement arms are shaped such thateach of the trough complexes includes exactly one trough.

in an embodiment, each of the engagement arms is configured to engage arespective one of the aortic sinuses upon implantation of theprosthesis.

There is still further provided, in accordance with an embodiment of thepresent invention, apparatus including a prosthesis for implantation ata native semilunar valve of a native valve complex of a subject, theprosthesis including:

a prosthetic valve including one or more prosthetic leaflets configuredto assume a closed position during diastole and an open position duringsystole; and

a valve prosthesis support, coupled to the prosthetic valve, andconfigured to engage one or more semilunar sinuses of the nativesemilunar valve site, such that at least 50% of an axial length of theprosthetic leaflets is distal to native valve leaflets of the nativesemilunar valve.

In an embodiment, the native semilunar valve includes a native aorticvalve, the semilunar sinuses include respective aortic sinuses, and thevalve prosthetic support is configured to engage the one or more aorticsinuses. In an embodiment, the native semilunar valve includes a nativepulmonary valve, the semilunar sinuses include respective pulmonarysinuses, and the valve prosthetic support is configured to engage theone or more pulmonary sinuses.

There is yet further provided, in accordance with an embodiment of thepresent invention, a method for implanting a prosthesis at a nativesemilunar valve of a native valve complex of a subject, the native valvecomplex having three semilunar sinuses and three native commissures, themethod including:

providing the prosthesis including a valve prosthesis support, whichvalve prosthesis support includes a support structure including exactlythree engagement arms that meet one another at three respectivejunctures, and the engagement arms are shaped so as define three peakcomplexes at the three respective junctures, and three trough complexes,each of which is between two of the peak complexes; and

implanting the prosthesis such that each of the engagement arms is atleast partially disposed within a respective one of the semilunarsinuses, each of the peak complexes is disposed distal to and inrotational alignment with a respective one of the native commissures,and each of the trough complexes is disposed at least partially withinthe respective one of the semilunar sinuses.

In an embodiment, the native semilunar valve includes a native aorticvalve of the subject, the semilunar sinuses include respective aorticsinuses, and implanting includes implanting the prosthesis such thateach of the engagement arms is disposed at least partially within therespective one of the aortic sinuses.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve of the subject, the semilunar sinuses include respective pulmonarysinuses, and implanting includes implanting the prosthesis such thateach of the engagement arms is disposed at least partially within therespective one of the pulmonary sinuses.

In an embodiment, the prosthesis is configured such that, duringimplantation of the prosthesis, the peak complexes self-align with therespective native commissures.

In an embodiment, implanting includes implanting the prosthesis suchthat the prosthesis embraces, such as gently embraces, withoutsqueezing, leaflets of the native semilunar valve. In an embodiment,implanting includes implanting the prosthesis such that the valveprosthesis support does not fold over leaflets of the native semilunarvalve.

In an embodiment, implanting includes implanting the prosthesis suchthat the engagement arms touch respective floors of the respectivesemilunar sinuses.

In an embodiment, implanting includes causing the prosthesis toself-align with respect to the native semilunar valve site by gentlyrotating the prosthesis.

In an embodiment, the support structure is configured to serve as adistal fixation member, the valve prosthesis support includes a proximalfixation member, and implanting includes implanting the prosthesis suchthat the proximal fixation member and the engagement arms of the distalfixation member axially sandwich the native valve complex fromventricular and downstream sides thereof, respectively.

In an embodiment, implanting includes:

positioning the distal fixation member in a downstream artery while thedistal fixation member is collapsed;

expanding the distal fixation member; and

thereafter, positioning the proximal fixation member at least partiallyon the ventricular side of the native valve complex, the downstreamartery selected from the group consisting of: an ascending aorta, and apulmonary trunk.

In an embodiment, implanting includes:

storing the proximal and distal fixation members in at least one tubeselected from the group consisting of: an overtube and a trocar, whilethe proximal and distal fixation members are collapsed; and

deploying the proximal and distal fixation members from the selectedtube such that the proximal and distal fixation members expand.

In an embodiment, the proximal fixation member includes an inner supportstructure, the distal fixation member includes an outer supportstructure that is placed partially over the inner support structure, andimplanting includes configuring the inner and outer support structuresto one another during the implanting.

There is additionally provided, in accordance with an embodiment of thepresent invention, a method for implanting a prosthesis at a nativeaortic valve of a native valve complex of a subject, the native valvecomplex having exactly two aortic sinuses and two native commissures,the method including:

providing the prosthesis including a valve prosthesis support, whichvalve prosthesis support includes a support structure including exactlytwo engagement arms that meet one another at two respective junctures,and the engagement arms are shaped so as define two peak complexes atthe two respective junctures, and two trough complexes, each of which isbetween the peak complexes; and

implanting the prosthesis such that each of the engagement arms is atleast partially disposed within a respective one of the aortic sinuses,each of the peak complexes is disposed distal to and in rotationalalignment with a respective one of the native commissures, and each ofthe trough complexes is disposed at least partially within therespective one of the aortic sinuses.

There is still additionally provided, in accordance with an embodimentof the present invention, a method for implanting a prosthesis at anative semilunar valve of a native valve complex of a subject, themethod including:

providing the prosthesis including a prosthetic valve including one ormore prosthetic leaflets configured to assume a closed position duringdiastole and an open position during systole, and a valve prosthesissupport, coupled to the prosthetic valve; and

implanting the prosthesis such that the valve prosthesis support engagesone or more semilunar sinuses of the native semilunar valve site, suchthat at least 50% of an axial length of the prosthetic leaflets isdistal to native valve leaflets of the native semilunar valve.

In an embodiment, the native semilunar valve includes a native aorticvalve, and implanting the prosthesis includes implanting the prosthesissuch that the valve prosthesis support engages the one or more semilunarsinuses of the native aortic valve.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, and implanting the prosthesis includes implanting the prosthesissuch that the valve prosthesis support engages the one or more semilunarsinuses of the native pulmonary valve.

In an embodiment, implanting the prosthesis includes implanting theprosthesis such that the prosthesis leaflets do not engage the semilunarsinuses.

In an embodiment, implanting the prosthesis includes causing theprosthesis to self-align with respect to the native semilunar valve siteby gently rotating the prosthesis.

There is yet additionally provided, in accordance with an embodiment ofthe present invention, a method, including:

placing a semilunar valve prosthesis at a native semilunar valve site,which prosthesis includes a prosthetic valve including one or moreprosthetic leaflets configured to assume a closed position duringdiastole and an open position during systole; and

engaging a portion of the semilunar valve prosthesis, other than theprosthetic leaflets, with one or more semilunar sinuses of the nativesemilunar valve site, such that at least 50% of an axial length of theprosthetic leaflets is distal to native valve leaflets of a nativesemilunar valve of the native semilunar valve site.

In an embodiment, the native semilunar valve site includes a nativeaortic valve site, the semilunar sinuses include respective aorticsinuses, the semilunar valve prosthesis includes an aortic valveprosthesis, placing includes placing the aortic valve prosthesis at thenative aortic valve site, and engaging includes engaging the portion ofthe aortic valve prosthesis with the one or more aortic sinuses.

In an embodiment, the native semilunar valve site includes a nativepulmonary valve site, the semilunar sinuses include respective pulmonarysinuses, the semilunar valve prosthesis includes a pulmonary valveprosthesis, placing includes placing the pulmonary valve prosthesis atthe native pulmonary valve site, and engaging includes engaging theportion of the pulmonary valve prosthesis with the one or more pulmonarysinuses.

In an embodiment, engaging includes causing the semilunar valveprosthesis to self-align with respect to the native semilunar valve siteby gently rotating the semilunar valve prosthesis.

There is also provided, in accordance with an embodiment of the presentinvention, apparatus including a prosthesis for implantation at a nativesemilunar valve of a native valve complex of a subject, the native valvecomplex having semilunar sinuses, the prosthesis including a valveprosthesis support, which includes a support structure including atleast two engagement arms, wherein, upon implantation of the prosthesis,each of the engagement arms is at least partially disposed within arespective one of the semilunar sinuses, and wherein a shape of at leastone of the engagement arms is generally characterized by a functionz″(r)>=0, where z is a height of any given point on the at least oneengagement arm measured along a longitudinal axis of the prosthesis, andr is a distance from the longitudinal axis to the given point.

For some applications, the shape is generally characterized by thefunction z″(r)>0.

In an embodiment, the native semilunar valve includes a native aorticvalve of the subject, the semilunar sinuses include respective aorticsinuses, and, upon implantation of the prosthesis, each of theengagement arms is disposed at least partially within the respective oneof the aortic sinuses.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve of the subject, the semilunar sinuses include respective pulmonarysinuses, and, upon implantation of the prosthesis, each of theengagement arms is at least partially disposed within the respective oneof the pulmonary sinuses.

For some applications, each of the engagement arms includes at least oneextension element that extends from the engagement arm, which at leastone extension element is configured to engage a sinus floor of therespective one of the semilunar sinuses upon implantation of theprosthesis.

In an embodiment, the support structure includes exactly threeengagement arms.

In an embodiment, the prosthesis is configured, upon implantationthereof, to embrace, such as gently embrace, without squeezing, leafletsof the native semilunar valve. In an embodiment, the valve prosthesissupport is configured such that, upon implantation of the prosthesis,the valve prosthesis support does not fold over leaflets of the nativesemilunar valve.

In an embodiment, the support structure is configured to serve as adistal fixation member, the valve prosthesis support includes a proximalfixation member, and the proximal fixation member and the engagementarms of the distal fixation member are configured to axially sandwichthe native valve complex from ventricular and downstream sides thereof,respectively, upon implantation of the prosthesis.

In an embodiment, each of the engagement arms is configured to engage arespective one of the semilunar sinuses upon implantation of theprosthesis.

For some applications, each of the engagement arms is shaped so as todefine at least one extension element that extends from the engagementarm, and each of the engagement arms and its respective at least oneextension element are configured such that the engagement arm engages,via the at least one extension element, a sinus floor of the respectiveone of the semilunar sinuses upon implantation of the prosthesis.

For some applications, each of the engagement arms is shaped to define alength, parallel to a longitudinal axis of the prosthesis, between (a)at least one of the junctures and (b) a contact point of one of theengagement arms that meets at the juncture with a sinus floor of therespective one of the semilunar sinuses upon implantation of theprosthesis, which length is greater than 6 mm.

In an embodiment, the prosthesis includes a prosthetic valve includingone or more prosthetic leaflets, at least a portion of each of theprosthetic leaflets is configured to assume a closed position duringdiastole and an open position during systole, and the at least a portionis not directly coupled to any of the engagement arms. For someapplications, the prosthetic valve is coupled to the support structuresuch that at least 50% of an axial length of the prosthetic leaflets isdistal to native valve leaflets of the native semilunar valve, uponimplantation of the prosthesis.

In an embodiment, the engagement arms are configured to touch respectivefloors of the respective semilunar sinuses, upon implantation of theprosthesis.

In an embodiment, the engagement arms are configured to firmly engagethe respective semilunar sinuses, upon implantation of the prosthesis.

There is further provided, in accordance with an embodiment of thepresent invention, apparatus including a prosthesis for implantation ata native semilunar valve of a native valve complex of a subject, thenative valve complex having semilunar sinuses, the prosthesis includinga valve prosthesis support, which includes a support structure includingat least two engagement arms,

wherein, upon implantation of the prosthesis, each of the engagementarms is at least partially disposed within a respective one of thesemilunar sinuses, and

wherein a shape of at least one of the engagement arms is generallyupwardly concave.

There is still further provided, in accordance with an embodiment of thepresent invention, a method for implanting a prosthesis at a nativesemilunar valve of a native valve complex of a subject, the native valvecomplex having semilunar sinuses, the method including:

providing the prosthesis including a valve prosthesis support, whichvalve prosthesis support includes a support structure including at leasttwo engagement arms, and a shape of at least one of the engagement armsis generally characterized by a function z″(r)>=0, where z is a heightof any given point on the at least one engagement arm measured along alongitudinal axis of the prosthesis, and r is a distance from thelongitudinal axis to the given point; and

implanting the prosthesis such that each of the engagement arms is atleast partially disposed within a respective one of the semilunarsinuses.

In an embodiment, implanting includes implanting the prosthesis suchthat each of the engagement arms is configured to engage a respectiveone of the semilunar sinuses.

There is yet further provided, in accordance with an embodiment of thepresent invention, a method for implanting a prosthesis at a nativesemilunar valve of a native valve complex of a subject, the native valvecomplex having semilunar sinuses, the method including:

providing the prosthesis including a valve prosthesis support, whichvalve prosthesis support includes a support structure including at leasttwo engagement arms, and a shape of at least one of the engagement armsis generally upwardly concave; and

implanting the prosthesis such that each of the engagement arms is atleast partially disposed within a respective one of the semilunarsinuses.

There is additionally provided, in accordance with an embodiment of thepresent invention, a method including:

providing a semilunar valve prosthesis; and

implanting the prosthesis without using any imaging techniques.

In an embodiment, providing the semilunar valve prosthesis includesproviding an aortic valve prosthesis. In an embodiment, providing thesemilunar valve prosthesis includes providing a pulmonary valveprosthesis.

In an embodiment, implanting includes: placing the prosthesis at asemilunar valve site.; and causing the prosthesis to self-align withrespect to the site by gently rotating the prosthesis.

In an embodiment, implanting the prosthesis includes determining acorrect rotational disposition of the prosthesis with respect to asemilunar valve site based on tactile feedback.

There is still additionally provided, in accordance with an embodimentof the present invention, a method including:

providing a semilunar valve prosthesis;

placing the prosthesis in a body of a subject; and

determining a correct rotational disposition of the prosthesis withrespect to a semilunar valve site based on tactile feedback.

In an embodiment, providing the semilunar valve prosthesis includesproviding an aortic valve prosthesis. In an embodiment, providing thesemilunar valve prosthesis includes providing a pulmonary valveprosthesis.

In an embodiment, placing the prosthesis includes placing the prosthesiswithout using any imaging techniques.

There is yet additionally provided, in accordance with an embodiment ofthe present invention, a method including:

placing a semilunar valve prosthesis at a native semilunar valve site;and

causing the prosthesis to self-align with respect to the site by gentlyrotating the valve prosthesis.

In an embodiment, the semilunar valve prosthesis includes an aorticvalve prosthesis, the native semilunar valve site includes a nativeaortic valve site, and placing includes placing the aortic valveprosthesis at the native aortic valve site. In an embodiment, thesemilunar valve prosthesis includes a pulmonary valve prosthesis, thenative semilunar valve site includes a native pulmonary valve site, andplacing includes placing the pulmonary valve prosthesis at the nativepulmonary valve site.

In an embodiment, causing the prosthesis to self-align includes movingthe prosthesis in an axial direction defined with respect to an axis ofa downstream artery, while gently rotating the prosthesis, thedownstream artery selected from the group consisting of: an ascendingaorta, and a pulmonary trunk.

In an embodiment, gently rotating the prosthesis includes moving theprosthesis in a proximal direction such that contact of the prosthesiswith tissue of the native semilunar valve site causes the rotating.

In an embodiment, placing the prosthesis and causing the prosthesis toself-align include placing the prosthesis and causing the prosthesis toself-align without using any imaging techniques.

In an embodiment, causing the prosthesis to self-align includesverifying that the prosthesis is properly aligned with respect to thesemilunar valve site by attempting to rotate the prosthesis with respectto the semilunar valve site.

In an embodiment, the prosthesis is shaped so as to define one or moreproximal engagement arms that are configured to be positioned at leastpartially within respective semilunar sinuses of the native semilunarvalve site, and causing the prosthesis to self-align includes causingthe engagement arms to self-align with respect to the respectivesemilunar sinuses.

In an embodiment, gently rotating the prosthesis includes moving theprosthesis in a proximal direction such that contact of one or more ofthe engagement arms with tissue of the native semilunar valve sitecauses the rotating.

In an embodiment, causing the prosthesis to self-align includesverifying that the engagement arms are properly placed with respect tothe semilunar valve site by attempting to rotate the engagement armswith respect to the semilunar valve site.

There is also provided, in accordance with an embodiment of the presentinvention, a method, including:

placing a semilunar valve prosthesis at a native semilunar valve site,the prosthesis shaped so as to define one or more proximal engagementarms;

attempting to position the engagement arms at least partially withinrespective semilunar sinuses of the native semilunar valve site; and

verifying that the engagement arms are properly placed with respect tothe semilunar valve site by attempting to rotate the engagement armswith respect to the semilunar valve site.

In an embodiment, the semilunar valve prosthesis includes an aorticvalve prosthesis, the native semilunar valve site includes a nativeaortic valve site, and placing includes placing the aortic valveprosthesis at the native aortic valve site.

In an embodiment, the semilunar valve prosthesis includes a pulmonaryvalve prosthesis, the native semilunar valve site includes a nativepulmonary valve site, and placing includes placing the pulmonary valveprosthesis at the native pulmonary valve site.

There is further provided, in accordance with an embodiment of thepresent invention, apparatus including a prosthesis for implantation ata native semilunar valve of a native valve complex of a subject, theprosthesis including a support structure, which is configured such thata correct rotational disposition of the prosthesis with respect to thenative semilunar valve can be determined based on tactile feedback.

There is still further provided, in accordance with an embodiment of thepresent invention, apparatus including a prosthesis for implantation ata native semilunar valve of a native valve complex of a subject, thenative valve complex having semilunar sinuses and native commissures,the prosthesis including:

a distal fixation member, configured to be positioned in a downstreamartery of the subject selected from the group consisting of: anascending aorta, and a pulmonary trunk, and shaped so as to defineexactly three proximal engagement arms that are configured to bepositioned at least partially within respective ones of the semilunarsinuses, and, in combination, to apply, to tissue that defines thesemilunar sinuses, a first axial force directed toward a ventricle ofthe subject; and

a proximal fixation member coupled to the distal fixation member, theproximal fixation member configured to be positioned at least partiallyon a ventricular side of the native semilunar valve, and to apply, tothe ventricular side of the native valve complex, a second axial forcedirected toward the downstream artery, such that application of thefirst and second forces couples the prosthesis to the native valvecomplex.

In an embodiment, the native semilunar valve includes a native aorticvalve, and the downstream artery includes the ascending aorta, thesemilunar sinuses include respective aortic sinuses, and the distalfixation member is configured to be positioned in the ascending aorta,and the proximal engagement arms are configured to be positioned atleast partially within the respective aortic sinuses.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, and the downstream artery includes the pulmonary trunk, and thesemilunar sinuses include respective pulmonary sinuses, and the distalfixation member is configured to be positioned in the pulmonary trunk,and the proximal engagement arms are configured to be positioned atleast partially within the respective pulmonary sinuses.

In an embodiment, the distal and proximal fixation members areconfigured to couple the prosthesis to the native valve complex byaxially sandwiching the native valve complex from a downstream side andthe ventricular side thereof, upon implantation of the prosthesis.

In an embodiment, the distal fixation member does not press upon thenative commissures upon implantation of the prosthesis.

In an embodiment, the prosthesis is configured to apply a radial forceof less than 0.5 pounds outwardly against the native semilunar valve. Inan embodiment, the prosthesis is configured to apply the first axialforce with a force of at least 40 g during diastole. In an embodiment,the prosthesis is configured to apply the second axial force with aforce of at least 1 g during systole.

In an embodiment, the prosthesis is configured such that any radialforce applied by the prosthesis outwardly against the native semilunarvalve is insufficient by itself to chronically maintain the prosthesisin position with respect to the native valve complex under conditions ofnormal cardiac motion.

In an embodiment, the prosthesis is configured, upon implantationthereof, to embrace, such as gently embrace, without squeezing, leafletsof the native semilunar valve.

In an embodiment, the distal fixation member is configured to bepositioned in the downstream artery during an implantation procedurebefore the proximal fixation member is positioned at least partially onthe ventricular side of the native valve complex.

In an embodiment, the distal fixation member is configured such that itdoes not fold over leaflets of the native semilunar valve uponimplantation of the prosthesis. In an embodiment, the distal fixationmember is configured such that it does not push leaflets of the nativesemilunar valve towards semilunar sinus floors of the native valvecomplex upon implantation of the prosthesis.

In an embodiment, each of the proximal engagement arms is shaped so asdefine at least one trough that is configured to be positioned at leastpartially within a respective one of the semilunar sinuses.

In an embodiment, the three engagement arms meet one another at threerespective junctures, the engagement arms are shaped so as define threepeak complexes at the three respective junctures, and three troughcomplexes, each of which is between two of the peak complexes, and uponimplantation of the prosthesis, at least a portion of each of the peakcomplexes is disposed distal to and in rotational alignment with arespective one of the native commissures, and each of the troughcomplexes is disposed at least partially within the respective one ofthe semilunar sinuses.

In an embodiment, the engagement arms are configured to be positioned,during an implantation procedure, at least partially within therespective ones of the semilunar sinuses before the proximal fixationmember is positioned at least partially on the ventricular side of thenative valve complex, such that the engagement arms prevent leaflets ofthe native valve complex from opening more than a predetermined desiredamount, the opening being because of force applied by the proximalfixation member to the leaflets.

In an embodiment, the proximal fixation member is configured to bepositioned at least partially in a ventricle of the subject uponimplantation of the prosthesis.

In an embodiment, the prosthesis is configured to apply the first axialforce such that a ratio of (a) the first axial force to (b) a radialforce applied outwardly by the prosthesis against the native semilunarvalve is greater than 1.5:1.

In an embodiment, the prosthesis is configured to less than fully openleaflets of the native valve complex when the prosthesis is implanted atthe native semilunar valve complex.

In an embodiment, the distal fixation member is configured to elevateleaflets of the native semilunar valve from within the semilunar sinusesupon implantation of the prosthesis.

In an embodiment, the distal fixation member is configured to apply thefirst axial force to respective roots of one or more leaflets of thenative valve complex. In an embodiment, the distal fixation member isconfigured to apply the first axial force to respective transitionsbetween respective semilunar sinus floors and one or more leaflets ofthe native valve complex.

In an embodiment, the prosthesis is configured to apply the first axialforce such that the ratio is greater than 3:1, such as greater than 6:1.

In an embodiment, the prosthesis is configured to apply the second axialforce such that a ratio of (a) the second axial force to (b) a radialforce applied outwardly by the prosthesis against the native semilunarvalve is greater than 1.5:1, such as greater than 3:1, e.g., greaterthan 6:1.

In an embodiment, the prosthesis includes a prosthetic valve configuredto assume a closed position during diastole and an open position duringsystole. In an embodiment, the prosthetic valve includes a collapsiblepliant material, configured to assume the open and closed positions.

In an embodiment, the distal and proximal fixation members and theprosthetic valve are configured to define a single flow field throughthe distal and proximal fixation members and the prosthetic valve.Alternatively, the distal and proximal fixation members and theprosthetic valve are configured to define a plurality of flow fieldsthrough the distal and proximal fixation members and the prostheticvalve.

In an embodiment, the prosthetic valve includes one or more prostheticleaflets, and the prosthetic valve is coupled to the prosthesis suchthat at least 50% of an axial length of the prosthetic leaflets isdistal to native valve leaflets of the native semilunar valve uponimplantation of the prosthesis.

In an embodiment, the distal fixation member is configured to apply thefirst axial force to one or more semilunar sinus floors of the nativevalve complex.

In an embodiment, the distal fixation member is configured not to applyforce to leaflets of the native semilunar valve.

In an embodiment, the proximal fixation member is shaped so as to defineat least one barb configured to apply a barb force to the ventricularside of the native valve complex. For some applications, the at leastone barb is configured to pierce the ventricular side of the nativevalve complex. Alternatively, the at least one barb is configured toprotrude into tissue of the ventricular side of the native valuecomplex, without piercing the tissue. For some applications, the distalfixation member is shaped so as to define at least one mating barb, andthe at least one barb of the proximal fixation member is Configured toengage the at least one mating barb, so as to help hold the prosthesisin place.

In an embodiment, the proximal and distal fixation members arecollapsible. For some applications, the distal fixation member isconfigured to be positioned, during an implantation procedure, in thedownstream artery while collapsed, and to be expanded before theproximal fixation member is positioned at least partially on theventricular side of the native valve complex. For some applications, theapparatus includes at least one tube selected from the group consistingof an overtube and a trocar, and the proximal and distal fixationmembers are configured to be stored in the selected tube whilecollapsed, and to expand upon being deployed from the selected tube.

In an embodiment, the proximal fixation member includes an inner supportstructure, and the distal fixation member includes an outer supportstructure that is placed partially over the inner support structure.

In an embodiment, the outer support structure is shaped so as to defineexactly three distal diverging strut supports, from which respectiveones of the proximal engagement arms extend radially outward.

In an embodiment, the prosthesis is configured such that, uponimplantation at the native valve complex, the engagement arms arealigned by rotation with respective ones of the semilunar sinuses.

In an embodiment, the prosthesis is configured such that, uponimplantation at the native valve complex, the strut supports are alignedwith respective ones of the native commissures.

In an embodiment, the prosthesis is configured such that the engagementarms self-align themselves by rotation during implantation of theprosthesis at the native valve complex.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts.

In an embodiment, the inner support structure is shaped so as to definea bulging proximal skirt, a proximal portion of which is configured toapply the second axial force. In an embodiment, the prosthesis includesa graft covering that covers at least a portion of the skirt.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts, and the skirt extends fromthe inner struts.

In an embodiment, the outer support structure is shaped so as to defineexactly three distal diverging strut supports, from which respectiveones of the proximal engagement arms extend radially outward, and eachof the strut supports is positioned over a respective one of the innerstruts.

In an embodiment, the engagement arms are positioned over a portion ofthe skirt.

In an embodiment, the prosthesis includes a valve including acollapsible pliant material, configured to assume a closed positionduring diastole and an open position during systole, and the pliantmaterial includes a plurality of segments, at least two of which arecoupled together by one of the strut supports and its respective one ofthe inner struts.

There is yet further provided, in accordance with an embodiment of thepresent invention, apparatus including a prosthesis for implantation ata native semilunar valve of a native valve complex of a subject, theprosthesis including:

a distal fixation member, configured to be positioned in a downstreamartery of the subject selected from the group consisting of: anascending aorta, and a pulmonary trunk, and to apply, to tissue thatdefines one or more semilunar sinuses of the native valve complex, afirst axial force directed toward a ventricle of the subject; and

a proximal fixation member coupled to the distal fixation member, theproximal fixation member configured to be positioned at least partiallyon a ventricular side of the native semilunar valve, and to apply, tothe ventricular side of the native valve complex, a second axial forcedirected toward the downstream artery, such that application of thefirst and second forces couples the prosthesis to the native valvecomplex.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, the semilunarsinuses include respective aortic sinuses, and the distal fixationmember is configured to be positioned in the ascending aorta, and toapply the first axial force to the tissue that defines the one or moreaortic sinuses.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, the semilunarsinuses include respective pulmonary sinuses, and the distal fixationmember is configured to be positioned in the pulmonary trunk, and toapply the first axial force to the tissue that defines the one or morepulmonary sinuses.

In an embodiment, the distal and proximal fixation members areconfigured to couple the prosthesis to the native valve: complex byaxially sandwiching the native valve complex from a downstream side andthe ventricular side thereof, upon implantation of the prosthesis.

In on embodiment, the distal fixation member does not press upon nativevalve commissures of the native semilunar valve upon implantation of theprosthesis.

In an embodiment, the prosthesis is configured to apply a radial forceof less than 0.5 pounds outwardly against the native semilunar valve. Inan embodiment, the prosthesis is configured to apply the first axialforce with a force of at least 40 g during diastole. In an embodiment,the prosthesis is configured to apply the second axial force with aforce of at least 1 g during systole.

In an embodiment, the prosthesis is configured such that any radialforce applied by the prosthesis outwardly against the native semilunarvalve is insufficient by itself to chronically maintain the prosthesisin position with respect to the native valve complex under conditions ofnormal cardiac motion.

In an embodiment, the prosthesis is configured, upon implantationthereof, to embrace, such as gently embrace, without squeezing, leafletsof the native semilunar valve.

In an embodiment, the distal fixation member is configured to bepositioned in the downstream artery during an implantation procedurebefore the proximal fixation member is positioned at least partially onthe ventricular side of the native valve complex.

In an embodiment, the distal fixation member is configured such that itdoes not fold over leaflets of the native semilunar valve uponimplantation of the prosthesis. In an embodiment, the distal fixationmember is configured such that it does not push leaflets of the nativesemilunar valve towards semilunar sinus floors of the native valvecomplex upon implantation of the prosthesis. In an embodiment, theprosthesis is configured to less than fully open leaflets of the nativevalve complex when the prosthesis is implanted at the native valvecomplex.

In an embodiment, the distal fixation member is configured to apply thefirst axial force to respective roots of one or more leaflets of thenative valve complex. In an embodiment, the distal fixation member isconfigured to apply the first axial force to respective transitionsbetween respective semilunar sinus floors and one or more leaflets ofthe native valve complex.

In an embodiment, the proximal fixation member is configured to bepositioned at least partially in a ventricle of the subject uponimplantation of the prosthesis.

In an embodiment, the prosthesis is configured to apply the first axialforce such that a ratio of (a) the first axial force to (b) a radialforce applied outwardly by the prosthesis against the native semilunarvalve is greater than 1.5:1, such as greater than 3:1, e.g., greaterthan 6:1.

In an embodiment, the prosthesis is configured to apply the second axialforce such that a ratio of (a) the second axial force to (b) a radialforce applied outwardly by the prosthesis against the native semilunarvalve is greater than 1.5:1, such as greater than 3:1, e.g., greaterthan 6:1.

In an embodiment, the prosthesis includes a prosthetic valve configuredto assume a closed position during diastole and an open position duringsystole. In an embodiment, the prosthetic valve includes a collapsiblepliant material, configured to assume the open and closed positions.

In an embodiment, the distal and proximal fixation members and theprosthetic valve are configured to define a single flow field throughthe distal and proximal fixation members and the prosthetic valve.Alternatively, the distal and proximal fixation members and theprosthetic valve are configured to define a plurality of flow fieldsthrough the distal and proximal fixation members and the prostheticvalve.

In an embodiment, the prosthetic valve includes one or more prostheticleaflets, and the prosthetic valve is coupled to the prosthesis suchthat at least 50% of an axial length of the prosthetic leaflets isdistal to native valve leaflets of the native semilunar valve uponimplantation of the prosthesis.

In an embodiment, the distal fixation member is configured to apply thefirst axial force to one or more semilunar sinus floors of the nativevalve complex.

In an embodiment, the distal fixation member is configured not to applyforce to leaflets of the native semilunar valve.

In an embodiment, the distal fixation member is shaped so as to defineone or more proximal engagement arms that are configured to bepositioned at least partially within respective ones of the semilunarsinuses, and, in combination, to apply the first axial force.

In an embodiment, the distal fixation member is shaped so as to defineexactly three proximal engagement arms.

In an embodiment, each of the proximal engagement arms is shaped so asdefine at least one trough that is configured to be positioned at leastpartially within a respective one of the semilunar sinuses.

In an embodiment, the three engagement arms meet one another at threerespective junctures, the engagement arms are shaped so as define threepeak complexes at the three respective junctures, and three troughcomplexes, each of which is between two, of the peak complexes, and uponimplantation of the prosthesis, at least a portion of each of the peaksis disposed distal to and in rotational alignment with a respectivenative commissure of the native semilunar valve, and each of the troughcomplexes is disposed at least partially within the respective one ofthe semilunar sinuses.

In an embodiment, the distal fixation member is shaped so as to defineexactly two proximal engagement arms.

In an embodiment, the engagement arms are configured to be positioned,during an implantation procedure, at least partially within therespective ones of the semilunar sinuses before the proximal fixationmember is positioned at least partially on the ventricular side of thenative valve complex, such that the engagement arms prevent leaflets ofthe native valve complex from opening more than a predetermined desiredamount, the opening being because of force applied by the proximalfixation member to the leaflets.

In an embodiment, the proximal fixation member is shaped so as to defineat least one barb configured to apply a barb force to the ventricularside of the native valve complex. For some applications, the at leastone barb is configured to pierce the ventricular side of the nativevalve complex. Alternatively, the at least one barb is configured toprotrude into tissue of the ventricular side of the native valuecomplex, without piercing the tissue. For some applications, the distalfixation member is shaped so as to define at least one mating barb, andthe at least one barb of the proximal fixation member is configured toengage the at least one mating barb, so as to help hold the prosthesisin place.

In an embodiment, the proximal and distal fixation members arecollapsible. For some applications, the distal fixation member isconfigured to be positioned, during an implantation procedure, in thedownstream artery while collapsed, and to be expanded before theproximal fixation member is positioned at least partially on theventricular side of the native valve complex. For some applications, theapparatus includes at least one tube selected from the group consistingof an overtube and a trocar, and the proximal and distal fixationmembers are configured to be stored in the selected tube whilecollapsed, and to expand upon being deployed from the selected tube.

In an embodiment, the proximal fixation member includes an inner supportstructure, and the distal fixation member includes an outer supportstructure that is placed partially over the inner support structure.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which a pluralityof proximal engagement arms extend radially outward.

In an embodiment, the prosthesis is configured such that, uponimplantation at the native valve complex, the engagement arms arealigned by rotation with respective ones of the semilunar sinuses.

In an embodiment, the prosthesis is configured such that, uponimplantation at the native valve complex, the strut supports are alignedwith respective commissures of the native valve complex.

In an embodiment, the prosthesis is configured such that the engagementarms self-align themselves by rotation during implantation of theprosthesis at the native valve complex.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts.

In an embodiment, the inner support structure is shaped so as to definea bulging proximal skirt, a proximal portion of which is configured toapply the second axial force. For some applications, the prosthesisincludes a graft covering that covers at least a portion of the skirt.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts, and the skirt extends fromthe inner struts.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which a pluralityof proximal engagement arms extend radially outward, and each of thestrut supports is positioned over a respective one of the inner struts.

In an embodiment, the engagement arms are positioned over a portion ofthe skirt.

In an embodiment, the prosthesis includes a valve including acollapsible pliant material, configured to assume a closed positionduring diastole and an open position during systole, and the pliantmaterial includes a plurality of segments, at least two of which arecoupled together by one of the strut supports and its respective one ofthe inner struts.

There is additionally provided, in accordance with an embodiment of thepresent invention, apparatus including a prosthesis for implantation ata native semilunar valve of a native valve complex of a subject, theprosthesis including:

a distal fixation member, configured to be positioned in a downstreamartery of the subject selected from the group consisting of: anascending aorta, and a pulmonary trunk, and to apply, to nativecommissures of the native semilunar valve, a first axial force directedtoward a ventricle of the subject, without applying any force to nativeleaflets of the native semilunar valve, and the distal fixation memberis configured to rotationally align with the native semilunar valve; and

a proximal fixation member coupled to the distal fixation member, theproximal fixation member configured to be positioned at least partiallyon a ventricular side of the native valve complex, and to apply a secondaxial force directed toward the downstream artery, such that applicationof the first and second forces couples the prosthesis to the nativevalve complex by axially sandwiching the native valve complex from adownstream side and the ventricular side thereof, upon implantation ofthe prosthesis.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, and thedistal fixation member is configured to be positioned in the ascendingaorta, and to apply the first axial force to the native commissures ofthe native aortic valve.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, and thedistal fixation member is configured to be positioned in the pulmonarytrunk, and to apply the first axial force to the native commissures ofthe native pulmonary valve.

In an embodiment, the distal fixation member is configured torotationally self-align with the native semilunar valve.

In an embodiment, the distal fixation member includes one or moreengagement arms that are positioned at least partially within respectivesemilunar sinuses, of the native valve complex, upon implantation of theprosthesis.

In an embodiment, the engagement arms are configured to apply respectiveforces to respective floors of the semilunar sinuses, upon implantationof the prosthesis.

In an embodiment, the engagement arms are configured not to apply anyforce to floors of the semilunar sinuses, upon implantation of theprosthesis.

There is still additionally provided, in accordance with an embodimentof the present invention, apparatus including a prosthesis forimplantation at a native semilunar valve of a native valve complex of asubject, the prosthesis including:

a distal fixation member, configured to be positioned in a downstreamartery of the subject selected from the group consisting of: anascending aorta, and a pulmonary trunk, and to apply a first axial forcedirected toward a ventricle of the subject; and

a proximal fixation member coupled to the distal fixation member, theproximal fixation member configured to be positioned at least partiallyon a ventricular side of the native valve complex, and to apply a secondaxial force directed toward the downstream artery, such that applicationof the first and second forces couples the prosthesis to the nativevalve complex by axially sandwiching the native valve complex from adownstream side and the ventricular side thereof,

wherein the prosthesis is configured to apply a radial force of lessthan 0.5 pounds outwardly against the native semilunar valve.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, and thedistal fixation member is configured to be positioned in the ascendingaorta.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, and thedistal fixation member is configured to be positioned in the pulmonarytrunk.

In an embodiment, the distal fixation member does not press upon nativevalve commissures of the native semilunar valve upon implantation of theprosthesis.

In an embodiment, the prosthesis is configured to apply the first axialforce such that a ratio of (a) the first axial force to (b) the radialforce is greater than 1.5:1. In an embodiment, the prosthesis isconfigured to apply the second axial force such that a ratio of (a) thesecond axial force to (b) the radial force is greater than 1.5:1. In anembodiment, the prosthesis is configured to apply the first axial forcewith a force of at least 40 g during diastole. In an embodiment, theprosthesis is configured to apply the second axial force with a force ofat least 1 g during systole.

In an embodiment, the prosthesis is configured such that any radialforce applied by the prosthesis outwardly against the native semilunarvalve is insufficient by itself to chronically maintain the prosthesisin position with respect to the native valve complex under conditions ofnormal cardiac motion.

In an embodiment, the prosthesis is configured, upon implantationthereof, to embrace, such as gently embrace, without squeezing, leafletsof the native semilunar valve. In an embodiment, the distal fixationmember is configured such that it does not fold over leaflets of thenative semilunar valve upon implantation of the prosthesis. In anembodiment, the prosthesis is configured to less than fully openleaflets of the native valve complex when the prosthesis is implanted atthe native valve complex.

In an embodiment, the proximal fixation member is configured to bepositioned at least partially in a ventricle of the subject uponimplantation of the prosthesis.

In an embodiment, the prosthesis includes a valve configured to assume aclosed position during diastole and an open position during systole. Inan embodiment, the valve includes a collapsible pliant material,configured to assume the open and closed positions.

In an embodiment, the distal and proximal fixation members and the valveare configured to define a single flow field through the distal andproximal fixation members and the valve. Alternatively, the distal andproximal fixation members and the valve are configured to define aplurality of flow fields through the distal and proximal fixationmembers and the valve.

In an embodiment, the valve includes one or more prosthetic leaflets,and the valve is coupled to the prosthesis such that at least 50% of anaxial length of the prosthetic leaflets is distal to native valveleaflets of the native semilunar valve upon implantation of theprosthesis.

In an embodiment, the proximal fixation member is shaped so as to defineat least one barb configured to apply a barb force to the ventricularside of the native valve complex. For some applications, the at leastone barb is configured to pierce the ventricular side of the nativevalve complex. Alternatively, the at least one barb is configured toprotrude into tissue of the ventricular side of the native valvecomplex, without piercing the tissue. For some applications, the distalfixation member is shaped so as to define at least one mating barb, andthe at least one barb of the proximal fixation member is configured toengage the at least one mating barb, so as to help hold the prosthesisin place.

In an embodiment, the proximal and distal fixation members arecollapsible. For some applications, the distal fixation member isconfigured to be positioned, during an implantation procedure, in thedownstream artery while collapsed, and to be expanded before theproximal fixation member is positioned at least partially on theventricular side of the native valve complex. For some applications, theapparatus includes at least one tube selected from the group consistingof: an overtube and a trocar, and the proximal and distal fixationmembers are configured to be stored in the selected tube whilecollapsed, and to expand upon being deployed from the selected tube.

In an embodiment, the proximal fixation member includes an inner supportstructure, and the distal fixation member includes an outer supportstructure that is placed partially over the inner support structure.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which a pluralityof proximal engagement arms extend radially outward.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts.

In an embodiment, the inner support structure is shaped so as to definea bulging proximal skirt, a proximal portion of which is configured toapply the second axial force. For some applications, the prosthesisincludes a graft covering that covers at least a portion of the skirt.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts, and the skirt extends fromthe inner struts.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which a pluralityof proximal engagement arms extend radially outward, and each of thestrut supports is positioned over a respective one of the inner struts.

In an embodiment, the engagement arms are positioned over a portion ofthe skirt.

In an embodiment, the prosthesis includes a valve including acollapsible pliant material, configured to assume a closed positionduring diastole and an open position during systole, and the pliantmaterial includes a plurality of segments, at least two of which arecoupled together by one of the strut supports and its respective one ofthe inner struts.

There is yet additionally provided, in accordance with an embodiment ofthe present invention, a method for implanting a valve prosthesis at anative semilunar valve of a native valve complex of a subject, themethod including:

providing a distal fixation member of the valve prosthesis coupled to aproximal fixation member of the valve prosthesis, which distal fixationmember is shaped so as to define exactly three proximal engagement arms;

positioning the distal fixation member in a downstream artery of thesubject selected from the group consisting of: an ascending aorta, and apulmonary trunk, such that the three proximal engagement arms arepositioned at least partially within respective semilunar sinuses of thenative valve complex, and, in combination, apply, to tissue that definesthe semilunar sinuses, a first axial force directed toward a ventricleof the subject; and

positioning the proximal fixation member at least partially on aventricular side of the native semilunar valve, such that the proximalfixation member applies, to the ventricular side of the native valvecomplex, a second axial force directed toward the downstream artery,such that application of the first and second forces couples theprosthesis to the native valve complex.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, andpositioning the distal fixation member includes positioning the distalfixation member in the ascending aorta.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, andpositioning the distal fixation member includes positioning the distalfixation member in the pulmonary trunk.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member before positioning the distal fixationmember and before positioning the proximal fixation member.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member after performing at least one actionselected from the group consisting of positioning the distal fixationmember, and positioning the proximal fixation member.

In an embodiment, the distal fixation member and the proximal fixationmember are fabricated as one integrated structure, and providing thedistal fixation member coupled to the proximal fixation member includesproviding the distal fixation member and the proximal fixation memberthat are fabricated as one integrated structure.

In an embodiment, positioning the distal and proximal fixation membersincludes positioning the engagement arms at least partially within therespective ones of the semilunar sinuses before positioning the proximalfixation member at least partially on the ventricular side of the nativevalve complex, such that the engagement arms prevent leaflets of thenative valve complex from opening more than a predetermined desiredamount, the opening being because of force applied by the proximalfixation member to the leaflets.

There is also provided, in accordance with an embodiment of the presentinvention, a method for implanting a valve prosthesis at a nativesemilunar valve of a native valve complex of a subject, the methodincluding:

providing a distal fixation member of the valve prosthesis coupled to aproximal fixation member of the valve prosthesis;

positioning the distal fixation member in a downstream artery of thesubject selected from the group consisting of: an ascending aorta, and apulmonary trunk, such that the distal fixation member applies, to adownstream side of the native valve complex, a first axial forcedirected toward a ventricle of the subject; and

positioning the proximal fixation member at least partially on aventricular side of the native semilunar valve, such that the proximalfixation member applies, to a ventricular side of the native semilunarvalve, a second axial force directed toward the downstream artery, suchthat application of the first and second forces couples the prosthesisto the native semilunar valve.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes: the ascending aorta, andpositioning the distal fixation member includes positioning the distalfixation member in the ascending aorta.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, andpositioning the distal fixation member includes positioning the distalfixation member in the pulmonary trunk.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member before positioning the distal fixationmember and before positioning the proximal fixation member.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member after performing at least one actionselected from the group consisting of: positioning the distal fixationmember, and positioning the proximal fixation member.

In an embodiment, the distal fixation member and the proximal fixationmember are fabricated as one integrated structure, and providing thedistal fixation member coupled to the proximal fixation member includesproviding the distal fixation member and the proximal fixation memberthat are fabricated as one integrated structure.

In an embodiment, positioning the distal and proximal fixation membersincludes positioning the distal fixation member in the downstream arterybefore positioning the proximal fixation member at least partially onthe ventricular side of the native semilunar valve.

In an embodiment, the prosthesis includes a prosthetic valve, andpositioning the distal fixation member includes positioning the distalfixation member such that the valve assumes a closed position duringdiastole and an open position during systole.

In an embodiment, positioning the distal fixation member includespositioning the distal fixation member such that it limits an extent ofopening of leaflets of the native valve complex.

In an embodiment, positioning the proximal and distal fixation membersincludes:

collapsing the proximal and distal fixation members;

inserting the proximal and distal fixation members, while collapsed, inthe ventricle and the downstream artery, respectively; and

expanding the proximal and distal fixation members in the ventricle andthe downstream artery, respectively.

In an embodiment, positioning the distal fixation member includespositioning the distal fixation member in the downstream artery whilecollapsed, and expanding the distal fixation member before positioningthe proximal fixation member at least partially on the ventricular sideof the native semilunar valve.

In an embodiment, inserting the proximal and distal fixation membersincludes storing the proximal and distal fixation members whilecollapsed in at least one tube selected from the group consisting of: anovertube and a trocar, and expanding the proximal and distal fixationmembers includes deploying the proximal and distal fixation members fromthe selected tube.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, and insertingthe proximal and distal fixation members includes inserting the selectedtube through an apex of a heart of the subject, and advancing theselected tube through the ventricle until a distal end of the selectedtube passes the native semilunar valve.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, and insertingthe proximal and distal fixation members includes inserting the selectedtube using a transaortic approach.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, the ventricleincludes a right ventricle, and inserting the proximal and distalfixation members includes inserting the selected tube through a freewall of the right ventricle, and advancing the selected tube through theright ventricle past a right ventricular outflow tract of the heartuntil a distal end of the selected tube passes the native pulmonaryvalve.

In an embodiment, the proximal fixation member includes an inner supportstructure, the distal fixation member includes an outer supportstructure that is placed partially over the inner support structure, andpositioning the proximal and distal fixation members includespositioning the inner and outer support structures, respectively.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which a pluralityof proximal engagement arms extend radially outward, and positioning theouter support structure includes rotationally aligning the engagementarms with respective ones of the semilunar sinuses.

In an embodiment, positioning the outer support structure includesrotationally aligning the strut supports with respective commissures ofthe native valve complex.

In an embodiment, aligning the engagement arms and the strut supportsincludes moving the outer support structure in a proximal direction,such that the engagement arms self-align with the respective ones of thesemilunar sinuses.

There is further provided, in accordance with an embodiment of thepresent invention, a method for implanting a valve prosthesis at anative semilunar valve of a native valve complex of a subject, themethod including:

providing a distal fixation member of the valve prosthesis coupled to aproximal fixation member of the valve prosthesis;

positioning the distal fixation member in a downstream artery of thesubject selected from the group consisting of: an ascending aorta, and apulmonary trunk, such that the distal fixation member applies, to nativecommissures of the native semilunar valve, a first axial force directedtoward a ventricle of the subject, without applying any force to nativeleaflets of the native semilunar valve;

causing the distal fixation member to rotationally align with the nativesemilunar valve by gently rotating the valve prosthesis; and

positioning the proximal fixation member at least partially on aventricular side of the native valve complex, such that the proximalfixation member applies a second axial force directed toward thedownstream artery, such that application of the first and second forcescouples the prosthesis to the native valve complex by axiallysandwiching the native valve complex from a downstream side and theventricular side thereof.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, andpositioning the distal fixation member includes positioning the distalfixation member in the ascending aorta.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, andpositioning the distal fixation member includes positioning the distalfixation member in the pulmonary trunk.

In an embodiment, causing the distal fixation member to align includescausing the distal fixation member to rotationally self-align with thenative semilunar valve.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member before positioning the distal fixationmember and before positioning the proximal fixation member.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member after performing at least one actionselected from the group consisting of: positioning the distal fixationmember, and positioning the proximal fixation member.

In an embodiment, the distal fixation member and the proximal fixationmember are fabricated as one integrated structure, and providing thedistal fixation member coupled to the proximal fixation member includesproviding the distal fixation member and the proximal fixation memberthat are fabricated as one integrated structure.

There is still further provided, in accordance with an embodiment of thepresent invention, a method for implanting a valve prosthesis at anative semilunar valve of a native valve complex of a subject, themethod including:

providing a distal fixation member of the valve prosthesis coupled to aproximal fixation member of the valve prosthesis;

positioning the distal fixation member in a downstream artery of thesubject selected from the group consisting of: an ascending aorta, and apulmonary trunk, such that the distal fixation member applies a firstaxial force directed toward a ventricle of the subject; and

positioning the proximal fixation member at least partially on aventricular side of the native valve complex, such that the proximalfixation member applies a second axial force directed toward thedownstream artery, such that application of the first and second forcescouples the prosthesis to the native valve complex by axiallysandwiching the native valve complex from a downstream side and theventricular side thereof, and the prosthesis applies a radial force ofless than 0.5 pounds outwardly against the native semilunar valve.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, andpositioning the distal fixation member includes positioning the distalfixation member in the ascending aorta.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, andpositioning the distal fixation member includes positioning the distalfixation member in the pulmonary trunk.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member before positioning the distal fixationmember and before positioning the proximal fixation member.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member after performing at least one actionselected from the group consisting of positioning the distal fixationmember, and positioning the proximal fixation member.

In an embodiment, the distal fixation member and the proximal fixationmember are fabricated as one integrated structure, and providing thedistal fixation member coupled to the proximal fixation member includesproviding the distal fixation member and the proximal fixation memberthat are fabricated as one integrated structure.

There is yet further provided, in accordance with an embodiment of thepresent invention, apparatus including a prosthesis for implantation ata native semilunar valve of a native valve complex of a subject, theprosthesis including:

a distal fixation member, configured to be positioned in a downstreamartery of the subject selected from the group consisting of: anascending aorta, and a pulmonary trunk, and to apply a first axial forcedirected toward a ventricle of the subject; and

a proximal fixation member coupled to the distal fixation member, theproximal fixation member configured to be positioned at least partiallyon a ventricular side of the native valve complex, and to apply a secondaxial force directed toward the downstream artery, such that applicationof the first and second forces couples the prosthesis to the nativevalve complex by axially sandwiching the native valve complex from adownstream side and the ventricular side thereof,

wherein the prosthesis is configured to apply the first axial force suchthat a ratio of (a) the first axial force to (b) a radial force appliedoutwardly by the prosthesis against the native semilunar valve isgreater than 1.5:1.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, and thedistal fixation member is configured to be positioned in the ascendingaorta.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, and thedistal fixation member is configured to be positioned in the pulmonarytrunk.

In an embodiment, the prosthesis is configured such that the radialforce is less than 0.5 pounds. In an embodiment, the distal fixationmember does not press upon native valve commissures of the nativesemilunar valve upon implantation of the prosthesis. In an embodiment,the prosthesis is configured to apply the first axial force with a forceof at least 40 g during diastole.

In an embodiment, the prosthesis is configured such that any radialforce applied by the prosthesis outwardly against the native semilunarvalve is insufficient by itself to chronically maintain the prosthesisin position with respect to the native valve complex under conditions ofnormal cardiac motion.

In an embodiment, the prosthesis is configured, upon implantationthereof, to embrace, such as gently embrace, without squeezing, leafletsof the native semilunar valve.

In an embodiment, the distal fixation member is configured such that itdoes not fold over leaflets of the native semilunar valve uponimplantation of the prosthesis. In an embodiment, the prosthesis isconfigured to less than fully open leaflets of the native valve complexwhen the prosthesis is implanted at the native valve complex.

In an embodiment, the proximal fixation member is configured to bepositioned at least partially in a ventricle of the subject uponimplantation of the prosthesis.

In an embodiment, the prosthesis is configured to apply the first axialforce such that the ratio is greater than 3:1, such as greater than 6:1.

In an embodiment, the prosthesis includes a valve configured to assume aclosed position during diastole and an open position during systole.

In an embodiment, the valve includes a collapsible pliant material,configured to assume the open and closed positions.

In an embodiment, the distal and proximal fixation members and the valveare configured to define a single flow field through the distal andproximal fixation members and the valve.

In an embodiment, the distal and proximal fixation members and the valveare configured to define a plurality of flow fields through the distaland proximal fixation members and the valve.

In an embodiment, the valve includes one or more prosthetic leaflets,and the valve is coupled to the prosthesis such that at least 50% of anaxial length of the prosthetic leaflets is distal to native valveleaflets of the native semilunar valve upon implantation of theprosthesis.

In an embodiment, the proximal fixation member is shaped so as to defineat least one barb configured to apply a barb force to the ventricularside of the native valve complex. For some applications, the at leastone barb is configured to pierce the ventricular side of the nativevalve complex. Alternatively, the at least one barb is configured toprotrude into tissue of the ventricular side of the native valvecomplex, without piercing the tissue. For some applications, the distalfixation member is shaped so as to define at least one mating barb, andthe at least one barb of the proximal fixation member is configured toengage the at least one mating barb, so as to help hold the prosthesisin place.

In an embodiment, the proximal and distal fixation members arecollapsible. For some applications, the distal fixation member isconfigured to be positioned, during an implantation procedure, in thedownstream artery while collapsed, and to be expanded before theproximal fixation member is positioned at least partially on theventricular side of the native valve complex. For some applications, theapparatus includes at least one tube selected from the group consistingof: an overtube and a trocar, and the proximal and distal fixationmembers are configured to be stored in the selected tube whilecollapsed, and to expand upon being deployed from the selected tube.

In an embodiment, the proximal fixation member includes an inner supportstructure, and the distal fixation member includes an outer supportstructure that is placed partially over the inner support structure.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which a pluralityof proximal engagement arms extend radially outward.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts.

In an embodiment, the at support structure is shaped so as to define abulging proximal skirt, a proximal portion of which is configured toapply the second axial force. For some applications, the prosthesisincludes a graft covering that covers at least a portion of the skirt.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts, and the skirt extends fromthe inner struts.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which a pluralityof proximal engagement arms extend radially outward, and each of thestrut supports is positioned over a respective one of the inner struts.

In an embodiment, the engagement arms are positioned over a portion ofthe skirt.

In an embodiment, the prosthesis includes a valve including acollapsible pliant material, configured to assume a closed positionduring diastole and an open position during systole, and the pliantmaterial includes a plurality of segments, at least two of which arecoupled together by one of the strut supports and its respective one ofthe inner struts.

There is additionally provided, in accordance with an embodiment of thepresent invention, apparatus including a prosthesis for implantation ata native semilunar valve of a native valve complex of a subject, theprosthesis including:

a distal fixation member, configured to be positioned in a downstreamartery of the subject selected from the group consisting of: anascending aorta, and a pulmonary trunk, and to apply a first axial forcedirected toward a ventricle of the subject; and

a proximal fixation member coupled to the distal fixation member, theproximal fixation member configured to be positioned at least partiallyon a ventricular side of the native valve complex, and to apply a secondaxial force directed toward the downstream artery, such that applicationof the first and second forces couples the prosthesis to the nativevalve complex by axially sandwiching the native valve complex from adownstream side and the ventricular side thereof,

wherein the prosthesis is configured such that any radial force appliedby the prosthesis outwardly against the native semilunar valve isinsufficient, by itself to chronically maintain the prosthesis inposition with respect to the native valve complex under conditions ofnormal cardiac motion.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, and thedistal fixation member is configured to be positioned in the ascendingaorta.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, and thedistal fixation member is configured to be positioned in the pulmonarytrunk.

In an embodiment, the prosthesis is configured to apply the first axialforce such that a ratio of (a) the first axial force to (b) the radialforce is greater than 1.5:1. In an embodiment, the prosthesis isconfigured to apply the second axial force such that a ratio of (a) thesecond axial force to (b) the radial force is greater than 1.5:1. In anembodiment, the prosthesis is configured such that the radial force isless than 0.5 pounds.

In an embodiment, the distal fixation member does not press upon nativevalve commissures of the native semilunar valve upon implantation of theprosthesis.

In an embodiment, the prosthesis is configured to apply the first axialforce with a force of at least 40 g during diastole. In an embodiment,the prosthesis is configured to apply the second axial force with aforce of at least 1 g during systole.

In an embodiment, the prosthesis is configured, upon implantationthereof, to embrace, such as gently embrace, without squeezing, leafletsof the native semilunar valve. In an embodiment, the distal fixationmember is configured such that it does not fold over leaflets of thenative semilunar valve upon implantation of the prosthesis. In anembodiment, the prosthesis is configured to less than fully openleaflets of the native valve complex when the prosthesis is implanted atthe native valve complex.

In an embodiment, the prosthesis includes a valve configured to assume aclosed position during diastole and an open position during systole. Inan embodiment, the valve includes a collapsible pliant material,configured to assume the open and closed positions.

In an embodiment, the distal and proximal fixation members and the valveare configured to define a single flow field through the distal andproximal fixation members and the valve. For some applications, thedistal and proximal fixation members and the valve are configured todefine a plurality of flow fields through the distal and proximalfixation members and the valve.

In an embodiment, the valve includes one or more prosthetic leaflets,and the valve is coupled to the prosthesis such that at least 50% of anaxial length of the prosthetic leaflets is distal to native valveleaflets of the native semilunar valve upon implantation of theprosthesis.

There is also provided, in accordance with an embodiment of the presentinvention, a method for implanting a valve prosthesis at a nativesemilunar valve of a native valve complex of a subject, the methodincluding:

providing a distal fixation member of the valve prosthesis coupled to aproximal fixation member of the valve prosthesis;

positioning the distal fixation member in a downstream artery of thesubject selected from the group consisting of: an ascending aorta, and apulmonary trunk, such that the distal fixation member applies a firstaxial force directed toward a ventricle of the subject, such that aratio of (a) the first axial force to (b) a radial force appliedoutwardly by the prosthesis against the native semilunar valve isgreater than 1.5:1; and

positioning the proximal fixation member at least partially on aventricular side of the native valve complex, such that the proximalfixation member applies a second axial force directed toward thedownstream artery, and application of the first and second forcescouples the prosthesis to the native valve complex by axiallysandwiching the native valve complex from a downstream side and theventricular side thereof.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, andpositioning the distal fixation member includes positioning the distalfixation member in the ascending aorta.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, andpositioning the distal fixation member includes positioning the distalfixation member in the pulmonary trunk.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member before positioning the distal fixationmember and before positioning the proximal fixation member.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member after performing at least one actionselected from the group consisting of positioning the distal fixationmember, and positioning the proximal fixation member.

In an embodiment, the distal fixation member and the proximal fixationmember are fabricated as one integrated structure, and providing thedistal fixation member coupled to the proximal fixation member includesproviding the distal fixation member and the proximal fixation memberthat are fabricated as one integrated structure.

There is still additionally provided, in accordance with an embodimentof the present invention, a method for implanting a valve prosthesis ata native semilunar valve of a native valve complex of a subject, themethod including:

providing a distal fixation member of the valve prosthesis coupled to aproximal fixation member of the valve prosthesis;

positioning the distal fixation member in a downstream artery of thesubject selected from the group consisting of: an ascending aorta, and apulmonary trunk, such that the distal fixation member applies a firstaxial force directed toward a ventricle of the subject; and

positioning the proximal fixation member at least partially on aventricular side of the native valve complex, such that the proximalfixation member applies a second axial force directed toward thedownstream artery, and application of the first and second forcescouples the prosthesis to the native valve complex by axiallysandwiching the native valve complex from a downstream side and theventricular side thereof,

wherein positioning the distal and proximal fixation members includespositioning the distal and proximal fixation members such that anyradial force applied by the prosthesis outwardly against the nativesemilunar valve is insufficient by itself to chronically maintain theprosthesis in position with respect to the native valve complex underconditions of normal cardiac motion.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, andpositioning the distal fixation member includes positioning the distalfixation member in the ascending aorta.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, andpositioning the distal fixation member includes positioning the distalfixation member in the pulmonary trunk.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member before positioning the distal fixationmember and before positioning the proximal fixation member.

In an embodiment, providing includes coupling the distal fixation memberto the proximal fixation member after performing at least one actionselected from the group consisting of: positioning the distal fixationmember, and positioning the proximal fixation member.

In an embodiment, the distal fixation member and the proximal fixationmember which are fabricated as one integrated structure, and providingthe distal fixation member coupled to the proximal fixation memberincludes providing the distal fixation member and the proximal fixationmember that are fabricated as one integrated structure.

There is yet additionally provided, in accordance with an embodiment ofthe present invention, apparatus including a prosthesis for implantationat a native semilunar valve of a native valve complex of a subject, theprosthesis including:

a distal fixation member, configured to be positioned in a downstreamartery of the subject selected from the group consisting of: anascending aorta, and a pulmonary trunk, and to apply a first axial forcedirected toward a ventricle of the subject; and

a proximal fixation member coupled to the distal fixation member, theproximal fixation member configured to be positioned at least partiallyon a ventricular side of the native valve complex, and to apply a secondaxial force directed toward the downstream artery, such that applicationof the first and second forces couples the prosthesis to the nativevalve complex by axially sandwiching the native valve complex from adownstream side and the ventricular side thereof,

wherein the prosthesis is configured, upon implantation thereof, toembrace, without squeezing, leaflets of the native semilunar valve.

In an embodiment, the prosthesis is configured, upon implantationthereof, to gently embrace, without squeezing, the leaflets of thenative semilunar valve.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, and thedistal fixation member is configured to be positioned in the ascendingaorta.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, the downstream artery includes the pulmonary trunk, and thedistal fixation member is configured to be positioned in the pulmonarytrunk.

In an embodiment, the prosthesis is configured such that any radialforce applied by the prosthesis outwardly against the native semilunarvalve is insufficient by itself to chronically maintain the prosthesisin position with respect to the native valve complex under conditions ofnormal cardiac motion.

In an embodiment; the prosthesis is configured to apply the first axialforce such that a ratio of (a) the first axial force to (b) a radialforce applied outwardly by the prosthesis against the native semilunarvalve is greater than 1.5:1. In an embodiment, the prosthesis isconfigured to apply the second axial force such that a ratio of (a) thesecond axial force to (b) a radial force applied outwardly by theprosthesis against the native semilunar valve is greater than 1.5:1.

In an embodiment, the prosthesis is configured to apply a radial forceof less than 0.5 pounds outwardly against the native semilunar valve.

In an embodiment, the distal fixation member does not press upon nativevalve commissures of the native semilunar valve upon implantation of theprosthesis.

In an embodiment, the prosthesis is configured to apply the first axialforce with a force of at least 40 g during diastole. In an embodiment,the prosthesis is configured to apply the second axial force with aforce of at least 1 g during systole.

In an embodiment, the prosthesis is configured such that any radialforce applied by the prosthesis outwardly against the native semilunarvalve is insufficient by itself to chronically maintain the prosthesisin position with respect to the native valve complex under conditions ofnormal cardiac motion.

In an embodiment, the distal fixation member is configured such that itdoes not fold over leaflets of the native semilunar valve uponimplantation of the prosthesis. In an embodiment, the prosthesis isconfigured to less than fully open leaflets of the native valve complexwhen the prosthesis is implanted at the native valve complex.

In an embodiment, the prosthesis includes a valve configured to assume aclosed position during diastole and an open position during systole. Inan embodiment, the valve includes a collapsible pliant material,configured to assume the open and closed positions.

In an embodiment, the distal and proximal fixation members and the valveare configured to define a single flow field through the distal andproximal fixation members and the valve. Alternatively, the distal andproximal fixation members and the valve are configured to define aplurality of flow fields through the distal and proximal fixationmembers and the valve.

In an embodiment, the valve includes one or more prosthetic leaflets,and the valve is coupled to the prosthesis such that at least 50% of anaxial length of the prosthetic leaflets is distal to native valveleaflets of the native semilunar valve upon implantation of theprosthesis.

There is also provided, in accordance with an embodiment of the presentinvention, apparatus including a valve prosthesis for implantation at anative semilunar valve of a subject, the prosthesis including:

one or more distal fixation members, which are configured to be coupledwithout suturing to the native semilunar valve such that the membersprevent opening of native leaflets of the native semilunar valve totheir maximum diameter; and

a pliant material coupled to at least one of the distal fixationmembers, the pliant material having a closed position and an openposition.

in an embodiment, the native semilunar valve includes a native aorticvalve, and the one or more distal fixation members are configured to becoupled with suturing to the native aortic valve. In an embodiment, thenative semilunar valve includes a native pulmonary valve, and the one ormore distal fixation members are configured to be coupled with suturingto the native pulmonary valve.

In an embodiment, the one or more distal fixation members are configuredto define a maximum extent of opening of the native leaflets.

In an embodiment, the one or more distal fixation members include atleast two distal fixation members, and the at least two distal fixationmembers are configured such that upon implantation of the prosthesis, atleast a portion of the native leaflets is positioned between the atleast two distal fixation members.

There is further provided, in accordance with an embodiment of thepresent invention, a method for implanting a valve prosthesis at anative semilunar valve of a native valve complex of a subject, themethod including:

providing a distal fixation member of the valve prosthesis coupled to aproximal fixation member of the valve prosthesis;

positioning the distal fixation member in a downstream artery of thesubject selected from the group consisting of: an ascending aorta, and apulmonary trunk, such that the distal fixation member applies a firstaxial force directed toward a ventricle of the subject; and

positioning the proximal fixation member at least partially on aventricular side of the native valve complex, such that the proximalfixation member applies a second axial force directed toward thedownstream artery, and application of the first and second forcescouples the prosthesis to the native valve complex by axiallysandwiching the native valve complex from a downstream side and theventricular side thereof,

wherein positioning the distal and proximal fixation members includespositioning the distal and proximal fixation members such that the valveprosthesis embraces, without squeezing, leaflets of the native semilunarvalve.

In an embodiment, the native semilunar valve includes a native aorticvalve, the downstream artery includes the ascending aorta, andpositioning the distal fixation member includes positioning the distalfixation member in the ascending aorta. In an embodiment, the nativesemilunar valve includes a native pulmonary valve, the downstream arteryincludes the pulmonary trunk, and positioning the distal fixation memberincludes positioning the distal fixation member in the pulmonary trunk.

In an embodiment, positioning the distal and proximal fixation membersincludes positioning the distal and proximal fixation members such thatthe valve prosthesis gently embraces, without squeezing, the leaflets ofthe native semilunar valve.

There is still further provided, in accordance with an embodiment of thepresent invention, a method for implanting a valve prosthesis at anative semilunar valve of a subject, the method including:

positioning one or more distal fixation members of the valve prosthesisin a vicinity of the native semilunar valve, and a pliant materialcoupled to at least one of the distal fixation members has a closedposition and an open position; and

without suturing, coupling the one or more distal fixation members tothe native semilunar valve such that the distal fixation members preventopening of native leaflets of the native semilunar valve to theirmaximum diameter.

In an embodiment, the native semilunar valve includes a native aorticvalve, and positioning includes positioning the one or more distalfixation members in the vicinity of the native aortic valve.

In an embodiment, the native semilunar valve includes a native pulmonaryvalve, and positioning includes positioning the one or more distalfixation members in the vicinity of the native pulmonary valve.

In an embodiment, positioning the one or more distal fixation membersincludes positioning the one or more distal fixation members to define amaximum extent of opening of the native leaflets.

In an embodiment, the one or more distal fixation members include atleast two distal fixation members, and positioning includes positioningthe at least two distal fixation members such that at least a portion ofthe native leaflets are positioned between the at least two distalfixation members.

There is further provided, in accordance with an embodiment of thepresent invention, apparatus including a prosthesis for implantation ata stenosed native aortic valve of a native valve complex of a subject,the prosthesis including:

a distal fixation member, configured to be positioned in an ascendingaorta of the subject, and to apply, to an aortic side of the nativevalve complex, a first axial force directed toward a left ventricle ofthe subject; and

a proximal fixation member coupled to the distal fixation member, theproximal fixation member configured to be positioned at least partiallyon a left-ventricular side of the native aortic valve, and to apply, toa left-ventricular side of the aortic annulus, a second axial forcedirected toward the ascending aorta, such that application of the firstand second forces couples the prosthesis to the native valve complex.

In an embodiment, the distal fixation member is configured to bepositioned in the ascending aorta during an implantation procedurebefore the proximal fixation member is positioned at least partially onthe left-ventricular side of the native aortic valve.

In an embodiment, the distal fixation member is configured such that itdoes not crimp, fold, or compress leaflets of the native aortic valveupon implantation of the prosthesis.

In an embodiment, the distal fixation member is configured such that itdoes not push leaflets of the native aortic valve towards aortic sinusfloors of the native valve complex upon implantation of the prosthesis.

In an embodiment, the prosthesis includes a valve configured to assume aclosed position during diastole and an open position during systole.

In an embodiment, the valve includes a collapsible pliant material,configured to assume the open and closed positions.

In an embodiment, the distal and proximal fixation members and the valveare configured to define a single flow field through the distal andproximal fixation members and the valve.

In an embodiment, the distal and proximal fixation members and the valveare configured to define a plurality of flow fields through the distaland proximal fixation members and the valve.

In an embodiment, the prosthesis is configured to not fully openleaflets of the native valve complex when the prosthesis is implanted atthe native aortic valve complex.

In an embodiment, the distal fixation member is configured to bepositioned within one or more aortic sinuses of the native valve complexupon implantation of the prosthesis.

In an embodiment, the distal fixation member is configured to elevateleaflets of the native aortic valve from within the one or more aorticsinuses upon implantation of the prosthesis.

In an embodiment, the distal fixation member is configured to apply thefirst axial force to respective roots of one or more leaflets of thenative valve complex.

In an embodiment, the distal fixation member is configured to apply thefirst axial force to respective transitions between respective aorticsinus floors and one or more leaflets of the native valve complex.

In an embodiment, the distal fixation member is configured to apply thefirst axial force to one or more aortic sinus floors of the native valvecomplex.

In an embodiment, the distal fixation member is shaped so as to defineone or more proximal engagement arms that are configured to bepositioned within respective ones of the aortic sinuses, and, incombination, to apply the first axial force.

In an embodiment, the arms are configured to be positioned, during animplantation procedure, within the respective ones of the aortic sinusesbefore the proximal fixation member is positioned at least partially onthe left-ventricular side of the native aortic valve, such that the armsprevent leaflets of the native valve complex from opening more than apredetermined desired amount because of force applied by the proximalfixation member to the leaflets.

In an embodiment, the proximal fixation member is configured to bepositioned at least partially in a left ventricle of the subject uponimplantation of the prosthesis.

In an embodiment, the proximal fixation member is shaped so as to defineat least one barb configured to apply a barb force to theleft-ventricular side of the aortic annulus.

In an embodiment, the at least one barb is configured to pierce theleft-ventricular side of the aortic annulus.

In an embodiment, the at least one barb is configured to protrude intotissue of the left-ventricular side of the aortic annulus, withoutpiercing the tissue.

In an embodiment, the distal fixation member is shaped so as to defineat least one mating barb, and the at least one barb of the proximalfixation member is configured to engage the at least one mating barb, soas to help hold the prosthesis in place.

In an embodiment, the proximal and distal fixation members arecollapsible.

In an embodiment, the distal fixation member is configured to bepositioned, during an implantation procedure, in the ascending aortawhile collapsed, and to be expanded before the proximal fixation memberis positioned at least partially on the left-ventricular side of thenative aortic valve.

In an embodiment, the apparatus includes at least one tube selected fromthe group consisting of: an overtube and a trocar, and the proximal anddistal fixation members are configured to be stored in the selected tubewhile collapsed, and to expand upon being deployed from the selectedtube.

In an embodiment, the proximal fixation member includes an inner supportstructure, and the distal fixation member includes an outer supportstructure that is placed partially over the inner support structure.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which a pluralityof proximal engagement arms extend radially outward.

In an embodiment, the prosthesis is configured such that, uponimplantation at the native valve complex, the engagement arms arealigned by rotation with respective ones of aortic sinuses of the nativevalve complex.

In an embodiment, the prosthesis is configured such that, uponimplantation at the native valve complex, the strut supports are alignedwith respective commissures of the native valve complex.

In an embodiment, the prosthesis is configured such that the engagementarms self-align themselves by rotation during implantation of theprosthesis at the native valve complex.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts.

In an embodiment, the inner support structure is shaped so as to definea bulging proximal skirt, a proximal portion of which is configured toapply the second axial force.

In an embodiment, the prosthesis includes a graft covering that coversat least a portion of the skirt.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts, and the skirt extends fromthe inner struts.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which a pluralityof proximal engagement arms extend radially outward, and each of thestrut supports is positioned over a respective one of the inner struts.

In an embodiment, the engagement arms are positioned over a portion ofthe skirt.

In an embodiment, the membrane includes a plurality of segments, atleast two of which are coupled together by one of the strut supports andits respective one of the inner struts.

There is further provided, in accordance with an embodiment of theinvention, apparatus including a valve prosthesis for implantation at astenosed native aortic valve of a subject, the prosthesis including:

-   -   one or more fixation members, which are configured to be coupled        without suturing to the native aortic valve such that the        members do not open native leaflets of the native aortic valve        to their maximum diameter; and    -   a membrane coupled to at least one of the fixation members, the        membrane having a closed position and an open position.

There is still further provided, in accordance with an embodiment of theinvention, a method for treating a stenosed native aortic valve of anative valve complex of a subject, the method including:

positioning a distal fixation member of a valve prosthesis in anascending aorta of the subject, such that the distal fixation memberapplies, to an aortic side of the native valve complex, a first axialforce directed toward a left ventricle of the subject; and

positioning a proximal fixation member of the prosthesis at leastpartially on a left-ventricular side of the native aortic valve, suchthat the proximal fixation member applies, to a left-ventricular side ofthe aortic annulus, a second axial force directed toward the ascendingaorta, such that application of the first and second forces couples theprosthesis to the native valve.

In an embodiment, positioning the distal and proximal fixation membersincludes positioning the distal fixation member in the ascending aortabefore positioning the proximal fixation member at least partially onthe left-ventricular side of the native aortic valve.

In an embodiment, positioning the distal fixation member includespositioning the distal fixation member such that it does not crimp,fold, or compress leaflets of the native aortic valve.

In an embodiment, positioning the distal fixation member includespositioning the distal fixation member such that it does not pushleaflets of the native aortic valve towards aortic sinus floors of thenative valve complex.

In an embodiment, the prosthesis includes a valve, and positioning thedistal fixation member includes positioning the distal fixation membersuch that the valve assumes a closed position during diastole and anopen position during systole.

In an embodiment, the valve includes a collapsible pliant material, andpositioning the distal fixation member includes positioning the distalfixation member such that the pliant material assumes the open andclosed positions.

In an embodiment, positioning the distal and proximal fixation membersand the valve includes positioning the distal and proximal fixationmembers and the valve such that the distal and proximal fixation membersand the valve define a single flow field through the distal and proximalfixation members and the valve.

In an embodiment, positioning the distal and proximal fixation membersand the valve includes positioning the distal and proximal fixationmembers and the valve such that the distal and proximal fixation membersand, the valve define a plurality of flow fields through the distal andproximal fixation members and the valve.

In an embodiment, positioning the distal fixation member includespositioning the distal fixation member such that it does not fully openleaflets of the native valve complex.

In an embodiment, positioning the distal fixation member includespositioning the distal fixation member within one or more aortic sinusesof the native valve complex.

In an embodiment, positioning the distal fixation member includespositioning the distal fixation member such that it elevates leaflets ofthe native aortic valve from within the one or more aortic sinuses.

In an embodiment, positioning the distal fixation member includespositioning the distal fixation member such that the distal fixationmember applies the first axial force to respective roots of one or moreleaflets of the native valve complex.

In an embodiment, positioning the distal fixation member includespositioning the distal fixation member such that the distal fixationmember applies the first axial force to respective transitions betweenrespective aortic sinus floors and one or more leaflets of the nativevalve complex.

In an embodiment, positioning the distal fixation member includespositioning the distal fixation member such that the distal fixationmember applies the first axial force to one or more aortic sinus floorsof the native valve complex.

In an embodiment, the distal fixation member is shaped so as to defineone or more proximal engagement arms, and positioning the distalfixation member includes positioning the engagement arms withinrespective ones of the aortic sinuses, such that the engagement armsapply the first axial force.

In an embodiment, positioning the arms includes positioning the armsbefore positioning the proximal fixation member, such that the armsprevent leaflets of the native valve complex from opening more than apredetermined desired amount because of force applied by the proximalfixation member to the leaflets.

In an embodiment, positioning the proximal fixation member includespositioning the proximal fixation member at least partially in a leftventricle of the subject.

In an embodiment, the proximal fixation member is shaped so, as todefine at least one barb, and positioning the proximal fixation memberincludes positioning the proximal fixation member applies a barb forceto the left-ventricular side of the aortic annulus.

In an embodiment, positioning the proximal fixation member includespositioning the proximal fixation member such that the at least one barbpierces the left-ventricular side of the aortic annulus.

In an embodiment, positioning the proximal fixation member includespositioning the proximal fixation member such that the at least one barbprotrudes into tissue of the left-ventricular side of the aorticannulus, without piercing the tissue.

In an embodiment, the distal fixation member is shaped so as to defineat least one mating barb, and positioning the proximal and distalfixation members includes engaging the at least one barb by the at leastone mating barb, so as to help hold the prosthesis in place.

In an embodiment, positioning the proximal and distal fixation membersincludes:

collapsing the proximal and distal fixation members;

inserting the proximal and distal fixation members, while collapsed, inthe left ventricle and the ascending aorta, respectively; and

expanding the proximal and distal fixation members in the left ventricleand the ascending aorta, respectively.

In an embodiment, positioning the distal fixation member includespositioning the distal fixation member in the ascending aorta whilecollapsed, and expanding the distal fixation member before positioningthe proximal fixation member at least partially on the left-ventricularside of the native aortic valve.

In an embodiment, inserting the proximal and distal fixation membersincludes storing the proximal and distal fixation members whilecollapsed in at least one tube selected from the group consisting of: anovertube and a trocar, and expanding the proximal and distal fixationmembers includes deploying the proximal and distal fixation members fromthe selected tube.

In an embodiment, inserting the proximal and distal fixation membersincludes inserting the selected tube through an apex of a heart of thesubject, and advancing the selected tube through the left ventricleuntil a distal end of the selected tube passes the native aortic valve.

In an embodiment, inserting the proximal and distal fixation membersincludes inserting the selected tube using a transaortic approach.

In an embodiment, the proximal fixation member includes an inner supportstructure, the distal fixation member includes an outer supportstructure that is placed partially over the inner support structure, andpositioning the proximal and distal fixation members includespositioning the inner and cuter support structures, respectively.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which a pluralityof proximal engagement arms extend radially outward, and positioning theouter support structure includes rotationally aligning the engagementarms with respective ones of the aortic sinuses.

In an embodiment, positioning the outer support structure includesrotationally aligning the strut supports with respective commissures ofthe native valve complex.

In an embodiment, aligning the engagement arms and the strut supportsincludes moving the outer support structure in a proximal direction,such that the engagement arms self-align with the respective ones of theaortic sinuses.

In an embodiment, the inner support structure is shaped so as to definea bulging proximal skirt, and positioning the inner support structureincludes positioning the inner support structure such that a proximalportion of the skirt applies the second axial force.

In an embodiment, the prosthesis includes a graft covering that coversat least a portion of the skirt, and positioning the inner supportstructure includes positioning the inner support structure including thegraft covering.

In an embodiment, the inner support structure is shaped so as to definea plurality of distal diverging inner struts, the skirt extends from theinner struts, and positioning the inner support structure includespositioning the inner support structure that is shaped so as to definethe plurality of distal diverging inner struts.

In an embodiment, the outer support structure is shaped so as to definea plurality of distal diverging strut supports, from which a pluralityof proximal engagement arms extend radially outward, each of the strutsupports is positioned over a respective one of the inner struts, andpositioning the outer support structure includes positioning the outersupport structure that is shaped so as to define the plurality of distaldiverging strut supports.

In an embodiment, the engagement arms are positioned over a portion ofthe skirt, and positioning the outer support structure includespositioning the outer support structure including the engagement armspositioned over the portion of the skirt.

There is yet further provided, in accordance with an embodiment of theinvention, a method for treating a stenosed native aortic valve of asubject, the method including:

positioning one or more fixation members of a valve prosthesis in avicinity of the native aortic valve, and a membrane coupled to at leastone, of the fixation members has a closed position and an open position;and

without suturing, coupling the one or more fixation members to thenative aortic valve such that the fixation members do not open nativeleaflets of the native aortic valve to their maximum diameter.

In some embodiments of the present invention, a fixation mechanism isprovided for implanting a stent-based valve prosthesis for treating anative stenosed valve, such as an aortic valve. The fixation mechanismtypically enables accurate positioning of the prosthesis in the nativevalve orifice in a guided self-aligning procedure, as well as safe andsecure deployment and fixation.

In some embodiments of the present invention, the fixation mechanismincludes one or more of the following components and/or features:

-   -   a distal (i.e., downstream) fixation member, which typically        includes a fixation frame. When the valve prosthesis is in a        collapsed position, the fixation frame is pressed against a body        of the valve prosthesis by insertion into an outer sheath (i.e.,        an overtube);    -   the downstream fixation frame is shaped so as to define aortic        sinus fixation arms, a number of which is typically equal to the        number of aortic sinuses of the native valve;    -   the arms are configured to flare out laterally, when released        from the outer sheath, to an angle with respect to a central        axis of the prosthesis. Typically, the angle is precisely        predefined by the design of the downstream fixation frame and        arms, said angle open in the upstream direction. For some        applications, the arms are shaped so as to curve outwards        laterally;    -   upon deployment at the bottom of the aortic sinuses, the        downstream fixation arms exert force largely or substantially        only in the direction of the left ventricle (i.e., an axial        force), and exert little or substantially no force in the radial        direction;    -   the downstream fixation arms engage with the downstream side of        the native valve leaflets, but not with the upstream side of the        native valve leaflets. As a result: (a) the arms limit the        opening motion of the native valve leaflets to the        above-mentioned angle (which is typically predefined), and (b)        the configuration of the arms enables the sequential entrapment        of the native valve leaflets, first, from the downstream side by        the fixation arms, and, second, from the upstream side, by a        proximal (i.e., upstream) fixation member, thereby sandwiching        the leaflets at the above-mentioned angle (which is typically        predefined) without crimping, folding over, or bending the        native leaflets;    -   the downstream fixation arms engage with an upstream portion of        the valve prosthesis to form a locking mechanism, which, for        some applications, includes barbs; and/or    -   divergent commissural struts which encompass at their distal end        an area larger than the native aortic orifice, so that the        struts help resist migration of the valve prosthesis in an        upstream direction (i.e., towards the left ventricle), and        contribute to exerting and enhancing axial force in an upstream        direction in a manner that increases with their outward        angulation and the downstream (aortic) pressure.

In some embodiments of the present invention, the valve prosthesis isimplanted using a transapical implantation procedure. An introducerovertube or trocar is inserted into the left ventricular apex using aSeldinger technique. Through this trocar, a delivery catheter onto whichthe collapsed valve prosthesis (covered by a sheath) is mounted, isadvanced into the ascending aorta. Withdrawal of the sheath causes thefixation arms to flare out laterally to an angle which is typicallypredetermined by design, and to open in an upstream direction.

Gentle withdrawal and rotation of the delivery catheter, onto which theprosthesis with the flared-out arms is mounted, causes the arms to slideinto the aortic sinuses, until the arms reach the bottom (anatomicinferior portion) of the sinuses. This rotational alignment occursbecause the three-dimensional geometry of the downstream fixation frame,including the extended aortic sinus fixation arms, conforms to thethree-dimensional geometry of the aortic valve and aortic root. In thisposition, the fixation arms engage with the downstream side of thenative valve leaflets, and not with the upstream side of the nativevalve leaflets. Such engagement limits the opening motion of the nativevalve leaflets to the above-mentioned angle (which is typicallypredefined), so that the native leaflets are not pushed against thecoronary arteries upon device release. In addition, such engagementprovides the proper conditions for sequentially entrapping the nativevalve leaflets first from the downstream side (by the fixation arms),and subsequently from the upstream side (by the bottom of the valveprosthesis), thereby sandwiching the leaflets at the angle (which istypically predefined), without crimping, folding over, or bending thenative leaflets.

Once the proper position of the arms at the bottom of the aortic sinusesis verified, the correct position for complete device release isautomatically achieved. The proper position may be verified, forexample, by (a) sensing an elastic resistance in the axial direction,and sensing that the device is rotationally locked in place, and/or (b)using imaging techniques such as fluoroscopy and/or ultrasound. Releaseof the device from the delivery catheter causes a lower inflow portionof the prosthesis to unfold and press against the upstream side of thenative leaflets, thereby engaging with the upstream fixation arms in theaortic sinuses. The upstream fixation arms serve as counterparts to thelower inflow portion of the prosthesis in a mechanism that locks thenative leaflets and the surrounding periannular tissue for fixation.

Device migration in the upstream direction (into the left ventricle) isprevented by (a) the aortic sinus fixation arms, which exert axialpressure against the bottom of the sinuses, and (b) the outwardlydirected angulation of the longitudinally-oriented commissural struts ofthe prosthesis. The angulation of the struts not only prevents migrationinto the left ventricle by itself, but, during systole, also by exertingleverage on the aortic sinus fixation arms, which is a function of thedegree of the angle and aortic pressure. Migration of the device in adownstream direction is prevented by the inflow part of the devicepressing against the periannular tissue surrounding the upstream side ofthe valve leaflets, and by the inflow part of the device engaging withthe fixation arms in a locking mechanism, which, for some applications,includes the use of barbs placed at the inflow section of the device inan upstream direction against the fixation arms.

In other embodiments of the present invention, the valve prosthesis isimplanted using another implantation technique, such as an antegradetransseptal technique, or a retrograde endovascular-percutaneoustechnique.

The present invention will be more fully understood from the followingdetailed description of embodiments thereof, taken together with thedrawings, in which;

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a fully-assembled valveprosthesis, in accordance with an embodiment of the present invention;

FIG. 2A is a schematic illustration of a collapsible outer supportstructure of the prosthesis of FIG. 1 prior to assembly with an innersupport structure of the prosthesis, in accordance with an embodiment ofthe present invention;

FIG. 2B is a schematic illustration of the collapsible inner supportstructure prior to assembly with the outer support structure of theprosthesis of FIG. 1, in accordance with an embodiment of the presentinvention;

FIGS. 2C and 2D are schematic illustrations of alternativeconfigurations of a portion of the prosthesis of FIG. 1, in accordancewith respective embodiments of the present invention;

FIG. 2E is a schematic illustration of another configuration of acollapsible outer support structure of the prosthesis of FIG. 1 prior toassembly with an inner support structure of the prosthesis, inaccordance with an embodiment of the present invention;

FIGS. 3A-E are schematic illustrations of additional configurations ofthe outer support structure of FIG. 2A, in accordance with respectiveembodiments of the present invention;

FIG. 3F is a schematic illustration of an additional configuration a theouter support structure of FIG. 2A, in accordance with an embodiment ofthe present invention;

FIG. 3G is a schematic illustration of a fully-assembled valveprosthesis that includes inner engagement arms of the configuration ofFIG. 3F, in accordance with an embodiment of the present invention;

FIGS. 4A-C are schematic illustrations of configurations for coupling apliant material to inner struts of the inner support structure of FIG.2B and strut supports of the outer support structure of FIG. 2A, inaccordance with respective embodiment of the present invention;

FIGS. 4D and 4E are side-view schematic illustrations of configurationsfor coupling the pliant material of FIGS. 4A-C to a graft covering, inaccordance with respective embodiments of the present invention;

FIGS. 5A-C, 6A-B, 7A-E, and 8A illustrate apparatus and a method forimplanting the valve prosthesis of FIG. 1 in a native stenosed valve ofa heart, in accordance with respective embodiments of the presentinvention;

FIGS. 8B-C illustrate the prosthesis of FIG. 1 in situ, in accordancewith respective embodiments of the present invention;

FIGS. 9A-G schematically illustrate a transaortic approach forimplanting the valve prosthesis of FIG. 1, in accordance with anembodiment of the present invention;

FIGS. 10A and 10B show the valve prosthesis of FIG. 1 in open (systolic)and closed (diastolic) positions, respectively, in accordance with anembodiment of the present invention;

FIGS. 11A-D illustrate several configurations for axially coupling thevalve prosthesis of FIG. 1 to the aortic annulus, in accordance withrespective embodiments of the present invention;

FIGS. 12A-G illustrate a holding device for holding the valve prosthesisof FIG. 1 prior to the implantation of the prosthesis, in accordancewith an embodiment of the present invention;

FIGS. 13A-D illustrate the loading of the valve prosthesis of FIG. 1into a tube from the holding device of FIGS. 12A-G, in accordance withan embodiment of the present invention;

FIG. 14 is a schematic illustration of a valve prosthesis placed in apulmonary valve, in accordance with an embodiment of the presentinvention;

FIG. 15 is a schematic anatomical illustration showing the location of anative valve complex, in accordance with an embodiment of the presentinvention;

FIGS. 16A-H schematically illustrate another transapical technique forimplanting the prosthesis of FIG. 1, in accordance with an embodiment ofthe present invention; and

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 is a schematic illustration of a fully-assembled valve prosthesis10, in accordance with an embodiment of the present invention. Valveprosthesis 10 comprises a collapsible inner support structure 12 thatserves as a proximal fixation member, and a collapsible outer supportstructure 14 that serves as a distal fixation member. Outer and innersupport structures 14 and 12 may be initially formed separately and thenjoined together, as shown, or may be formed as one integrated structure,i.e., not formed separately and then joined together. For someapplications, outer and inner support structures 14 and 12 are joinedtogether prior to implantation of prosthesis 10 (during a manufacturingprocess, or by a healthcare worker prior to implantation), while forother applications, the outer and inner support structures are coupledto one another during an implantation procedure. For some applications,outer support structure 14 is constructed from a plurality of separatepieces, which are joined to inner support structure 12 using standardmanufacturing means, such as welding, gluing, or suturing (configurationnot shown), such that the functionality of outer support structure 14 isattained.

Valve prosthesis 10 is configured to be placed in a native diseasedvalve of a subject, such as a native stenotic aortic or pulmonary valve,using a minimally-invasive approach, such as a beating heart transapicalprocedure, such as described hereinbelow with reference to FIGS. 5A-8Aor with reference to FIGS. 16A-H, or a retrograde transaortic procedure,such as described hereinbelow with reference to FIGS. 9A-G. As used inthe present application, including in the claims, a “native semilunarvalve” is to be understood as including: (a) native semilunar valvesthat include their native leaflets, and (b) native semilunar valves, thenative leaflets of which have been surgically excised or are otherwiseabsent.

Reference is made to FIG. 2A, which is a schematic illustration ofcollapsible outer support structure 14 prior to assembly with innersupport structure 12, in accordance with an embodiment of the presentinvention. Outer support structure 14 is shaped so as to define aplurality of distal diverging strut supports 20, from which a pluralityof proximal engagement arms 22 extend radially outward in a proximaldirection. Typically, the engagement arms have a shape that is generallyupwardly concave, such as described hereinbelow with reference to FIG.17.

Although three strut supports 20 and engagement arms 22 are shown in thefigures, for some applications valve prosthesis 10 comprises fewer ormore supports and/or arms, such as two supports and two arms. It isnoted that approximately 90% of humans have exactly three aorticsinuses. The three supports and/or arms provided in most embodimentscorrespond to these three aortic sinuses. For implantation in theapproximately 10% of patients that have exactly two aortic sinuses,prosthesis 10 typically includes exactly two supports and/or arms.

Engagement arms 22 are typically configured to be at least partiallydisposed within aortic sinuses of the subject, and, for someapplications, to engage and/or rest against floors of the aorticsinuses, and to apply an axial force directed toward a left ventricle ofthe subject. Engagement arms 22 meet one another at respective junctures24. For applications in which each of engagements arms 22 is fabricatedas a separate piece, the engagement arms are mechanically engaged to oneanother where they meet at respective junctures 24. For someapplications, engagement arms 22 meet one another without actuallytouching one another, and instead meet via an area defined at eachrespective juncture 24. Typically, the engagement arms are configured todefine respective peaks at junctures 24 (or peak complexes, as describedhereinbelow with reference to FIG. 3E), and respective troughs 26between each two of the peaks (or trough complexes, as describedhereinbelow with reference to FIG. 3E).

Outer support structure 14 comprises a suitable material that allowsmechanical deformations associated with crimping and expansion of valveprosthesis 10, such as, but not limited to, nitinol or a stainless steelalloy (e.g., AISI 316). Outer support structure 14 is fabricated from asingle piece or from a plurality of parts that are coupled together(e.g., by suturing). For some applications, placement of engagement arms22 within the aortic sinuses prevents “device migration,” i.e.,undesired retrograde movement of valve prosthesis 10 that may resultfrom fluid forces applied to the valve. For some applications,engagement arms 22 are coated with a flexible material (e.g., polyester,biocompatible, synthetic, and/or pericardium).

Strut supports 20 and engagement arms 22 may be formed as one integratedstructure (as shown), or, alternatively, may be initially formedseparately and then joined to one another. For example, the strutsupport and arms may be mechanically interlocked or sutured together, orcoupled by other means. Typically, the strut support and arms are joinedprior to implantation.

Reference is made to FIG. 2B, which is a schematic illustration ofcollapsible inner support structure 12 prior to assembly with outersupport structure 14, in accordance with an embodiment of the presentinvention. For some applications, inner support structure 12 is shapedso as to define a plurality of distal diverging inner struts 30, and abulging proximal skirt 32 that extends from the struts. A proximalportion 34 of proximal skirt 32 is configured to engage a leftventricular outflow tract (LVOT) of the subject and/or periannulartissue at the top of the left ventricle. A relatively narrow throatsection 36 of proximal skirt 32 is configured to be positioned at avalvular annulus of the subject, and to engage the native valveleaflets. Inner support structure 12 comprises, for example, nitinol, astainless steel alloy, another metal, or another biocompatible material.

Reference is again made to FIG. 1. Inner and outer support structures 12and 14 are assembled together by placing outer support structure 14 overinner support structure 12, such that outer strut supports 20 arealigned with, and typically support, respective inner struts 30, andengagement arms 22 are placed over a portion of proximal skirt 32. Innerstruts 30 and outer strut supports 20 together function as commissuralposts. Typically, such assembly is performed prior to implantation ofprosthesis 10, such as during manufacture of the prosthesis;alternatively, such assembly is performed in vivo during an implantationprocedure, or prior to implantation by a healthcare worker.

Valve prosthesis 10 typically comprises a prosthetic distal valve 104,which typically comprises a pliant material 105 coupled to strutsupports 20 and/or inner struts 30. Pliant material 105 of valve 104 isconfigured to collapse inwardly (i.e., towards a longitudinal axis ofvalve prosthesis 10) during diastole, in order to inhibit retrogradeblood flow, and to open outwardly during systole, to allow blood flowthrough the prosthesis. For some applications, when in an open position,valve 104 assumes a diverging shape that causes blood to flowtherethrough with pressure recovery at a distal outlet of the valve, forexample using techniques described in one or more of the above-mentionedpatent application publications to Schwammenthal et al. For otherapplications, the shape of the valve does not cause such pressurerecovery. For example, an angle between the pliant material 105 and acentral longitudinal axis of prosthesis 10 may be too great to causepressure recovery. In this latter case, the large angle may serveexclusively, or at least in part, to help provide axial fixation ofprosthesis 10 to the native valve complex. Regardless of whetherpressure recovery is achieved, the angle between pliant Material 105 andthe central longitudinal axis of prosthesis 10 typically inhibitsmigration of the device in an upstream direction.

Pliant material 105 comprises a flexible supple material, such as aninert biological material, e.g., pericardium sheet or any medically safeelastomer, such as, but not limited to, polyester, polymer, a metallicmaterial/alloy, polyurethane, latex, or synthetic rubber. For someapplications, pliant material 105 is coupled to strut supports 20 and/orinner struts 30 by sewing, such as described hereinbelow with referenceto FIG. 4. For example, pliant material 105 may be sewn onto outerdiverging strut supports 20. Valve 104 comprises a single piece ormultiple pieces of pliant material 105 (e.g., leaflets) joined togetherto give a desired shape, typically a distally diverging shape. For someapplications, the pliant material and support structures are coupled toone another in a single-step procedure (e.g., by sewing all the piecestogether); alternatively, the pliant material and support structures arecoupled to one another in a plurality of sequential steps.

Typically, valve prosthesis 10 further comprises a graft covering 106which is coupled to proximal skirt 32, such as by sewing the coveringwithin the skirt (configuration shown in FIG. 1) or around the skirt(configuration not shown). Inner support structure 12 thus defines acentral structured body for flow passage that proximally terminates in aflared inlet (proximal skirt 32) that is configured to be seated withinan LVOT immediately below an aortic annulus/aortic valve. For someapplications, graft covering 106 is coupled at one or more sites topliant material 105.

FIGS. 2C and 2D are schematic illustrations of alternativeconfigurations of a portion of valve prosthesis 10, in accordance withrespective embodiments of the present invention. In theseconfigurations, inner support structure 12 and outer support structure14 are replaced by an element 38, which is shaped so as to define firstand second portions 40 and 42. First portions 40 serve as supportstructures, each of which functionally corresponds to a pair of strutsupport 20 and inner strut 30, described hereinabove with reference toFIGS. 2A and 28. Pliant material 105 is coupled to support structures40. Second portions 42 are bent in a proximal direction, such thatproximal portions of the second portions define respective engagementarms 22.

In the configuration shown in FIG. 2C, two second portions 42 extendfrom the distal end of each first portion 40. In the configuration shownin FIG. 2D, element 38 is shaped so as to define two shoulders 44 thatextend laterally from each first portion 40. A single second portion 42extends from each of shoulders 44.

Reference is again made to FIG. 1. In an embodiment of the presentinvention, inner support structure 12 is shaped so as to define one ormore barbs 120, which are configured to pierce or protrude into theventricular side of the aortic annulus, as described hereinbelow withreference to FIGS. 7A-E. For some applications, one or more of innerstruts 30 is shaped so as to define a respective barb, while for otherapplications, another element of valve prosthesis 10 is shaped so as todefine the one or more barbs, such as proximal skirt 32. For someapplications, barbs 120 are oriented parallel to a longitudinal axis ofvalve prosthesis 10, while for other applications, barbs 120 areoriented to form an angle with respect to the longitudinal axis, such asbetween about −20 degrees (i.e., slanted towards a central axis of thenative valve) and about +89 degrees (i.e., slanted away from the centralaxis of the native valve), such as between about −5 and about +30degrees. For some applications, barbs 120 are set at the desired angleby heat-setting.

Reference is made to FIG. 2E, which is a schematic illustration ofanother configuration of collapsible outer support structure 14 prior toassembly with inner support structure 12, in accordance with anembodiment of the present invention. Inter-strut support elements 17 arecoupled between adjacent ones of distal diverging strut supports 20, andtypically serve to help maintain a desired distance between each ofstrut supports 20. For example, if a force is applied that would bringcloser or separate two of the strut supports, the inter-strut supportelement between the strut supports would tend to reduce such adeformation. For some applications, one or more of support elements 17is shaped so as to define a kink or curved section 19, which deformsslightly in response to force applied to element 17.

Reference is made to FIGS. 3A-E, which are schematic illustrations ofadditional configurations of outer support structure 14, in accordancewith respective embodiments of the present invention. In theconfigurations shown in FIGS. 3A-B, outer support structure 14 is shapedso as to define one or more native valve support elements 122. Thesesupport elements apply pressure to an outer (downstream) surface of thenative valve when engagement arms 22 are positioned in the aorticsinuses, so, as to hold the native leaflets in place against proximalskirt 32. In the configuration shown in FIG. 3A, the area defined byengagement arms 22 and support elements 122 is open, while in theconfiguration shown in FIG. 3B, a covering 124 is provided in this area.The covering generally may help capture calcific, thrombotic, or othermaterial which might be dislodged from the native valve or thesurrounding tissue, and may comprise, for example, polyester. In theconfiguration shown in FIG. 3C, covering 124 is provided without supportelements 122.

In the configuration shown in FIG. 3D, each of engagement arms 22comprises or is shaped so as to define at least one extension element 23that extends from the engagement arm. The engagement arms and extensionelements are configured such that the engagement arms engage and/or restagainst the floors of the aortic sinuses via the extension elements. Forsome applications, such as shown in FIG. 3D, exactly one extensionelement 23 extends from each of engagement arms 22, while for otherapplications, more than one extension element 23 extends from eachengagement arm (configuration not shown). Although engagement arms 22are shown in FIG. 3D as curving down toward the sinus floors, for someapplications the engagement arms are shaped so as to remain above thenative commissures (for example, the engagement arms collectively may beannular in shape), or to curve down less than is shown in FIG. 3D.

In the configuration shown in FIG. 3E, each of engagement arms 22 isshaped so as to define a plurality of troughs 25 and local peaks 27,rather than a single trough 26, as shown in FIG. 2A. In addition, eachof engagement arms 22 is shaped so as to define a plurality of peaks 29and local troughs 31, rather than a single peak at each of junctures 24,as shown in FIG. 2A. (Outer support structure 14 may include both, onlyone of, or neither of the features described in the preceding twosentences.) As used in the present application, including in the claims,a “trough complex” means a portion of an engagement arm that extendsdownwards between respective “peak complexes.” Each “trough complex”includes n local troughs 25 and n−1 local peaks 29, where n is greaterthan or equal to one. Each “peak complex” includes m local peaks 29 andn−1 local troughs 31, where m is greater than or equal to one. It isnoted that the portion of a peak complex that is at a juncture maydefine a local trough (configuration not shown). In addition, althoughthe peak and trough complexes shown in FIG. 3E are generallysymmetrical, non-symmetrical arrangements are also within the scope ofthe present invention.

For some applications, respective extension elements 23, describedhereinabove with reference to. FIG. 3D, extend from one or more of thetroughs of a trough complex, and/or from elsewhere along the troughcomplex.

FIG. 3F is a schematic illustration of an additional configuration ofouter support structure 14, in accordance with an embodiment of thepresent invention. In this embodiment, outer support structure 14, inaddition to defining proximal engagement arms 22, is shaped so as todefine a plurality of inner engagement arms 33. The inner engagementarms are configured to pass through the valvular annulus. Typically,troughs 35 of inner engagement arms 33 are configured to engage the LVOTand/or periannular tissue at the top of the left ventricle. For someapplications, each of inner engagement arms 33 is shaped so as to defineone or more barbs 37, which are configured to pierce or protrude intothe ventricular side of the aortic annulus. Typically, during animplantation procedure, inner engagement arms 33 are released from anovertube, trocar, or catheter prior to the release of proximal skirt 32therefrom, such as described hereinbelow with reference to FIGS. 7A-C,9A-G, and 16A-H. The fixation provided by inner engagement arms 33 holdsprosthesis 10 in place until the implantation procedure is complete,such that blood flow against skirt 32 does not dislodge the prosthesisduring the implantation procedure.

FIG. 3G is a schematic illustration of a fully-assembled valveprosthesis that includes inner engagement arms 33 of FIG. 3F, inaccordance with an embodiment of the present invention. FIG. 7E,described hereinbelow, shows prosthesis 10 in situ having theconfiguration shown in FIG. 3F.

For some applications, the features shown in one or more of FIGS. 2A-Band 3A-G are combined. For example, valve support elements 122 and/orcovering 124 may be provided for arms 22 of FIG. 3E. Other suchcombinations of features are within the scope of the present invention.

Reference is now made to FIGS. 4A-C, which are schematic illustrationsof configurations for coupling pliant material 105 to inner struts 30 ofinner support structure 12 and to strut supports 20 of outer supportstructure 14, in accordance with respective embodiments of the presentinvention.

In the configuration shown in FIG. 4A, valve 104 comprises a pluralityof segments of pliant material 105, pairs of which are coupled togetherat respective interfaces between one of inner struts 30 and one of strutsupports 20. Inner strut 30 is shaped so as to define an elongated slit130. During manufacture of valve prosthesis 10, edges of two pieces ofpliant material 105 are inserted through slit 130 such that a portion ofeach of the pieces of pliant material is sandwiched between inner strut30 and strut support 20. The inner strut and strut support are tightlycoupled together, such as by passing one or more sutures 132 throughholes 134 defined by inner strut 30 and strut support 20. Sutures 132typically couple the strut and strut support together such that pliantmaterial 105 is supported on both sides thereof, thereby forming astrain relief which reduces stresses on the leaflets of valve 104 at thesutures. The relatively large surface areas of inner strut 30 and strutsupport 20 distribute the stress applied at pliant material 105, so thatthis stress is not applied primarily around holes 134. Typically, theedges of slit 130 are rounded in order to avoid damage to pliantmaterial 105.

In the configuration shown in FIGS. 4B-C, portions 136 of graft covering106 (including, optionally, pericardium or any suitable supple syntheticor biological material) are inserted through slit 130, between the edgesof the slit and the two pieces of pliant material. The portions of thegraft covering reduce friction between the pliant material and innerstrut 30. As can be seen in FIG. 4C, portions 136 of graft covering 106are typically integral with the rest of graft covering 106 (which issewn to skirt 32). Graft covering 106 (including, optionally,pericardium or any suitable supple synthetic or biological material) isthus shaped so as to define distally protruding portions 136.

FIGS. 4D and 4E are side-view schematic illustrations of twoconfigurations for coupling pliant material 105 to graft covering 106,and reducing leaflet stress during valve opening (FIG. 4D) or valveclosure (FIG. 4E), in accordance with respective embodiments of thepresent invention. In both of these configurations, graft covering 106is sewn to a cord 107, such that a portion of pliant material 105 isheld between the cord and the graft covering. Cord 107 passes through ahole 108 (FIG. 4C) passing through or near one of the commissural posts(configuration not shown).

Reference is now made to FIGS. 5A-8A, which illustrate apparatus and amethod for implanting valve prosthesis 10 in a native stenosed valve 140of a heart 142, in accordance with respective embodiments of the presentinvention.

FIGS. 5A-C illustrate an overtube or trocar 150 and the initial steps ofthe implantation method, in accordance with respective embodiments ofthe present invention. Overtube or trocar 150 is placed over a dilator154. As shown in FIG. 5A, overtube or trocar 150 is typically insertedthrough an apex 156 of heart 142, and advanced into a left ventricle 157where its motion is terminated, or through left ventricle 157 until thedistal end of dilator 154 passes native aortic valve leaflets 158. Forexample, apex 156 may be punctured using a standard. Seldingertechnique, and a guidewire may be advanced into an ascending aorta 160.Optionally, native aortic valve 140 is partially dilated to about 15-20mm (e.g., about 16 mm), typically using a standard valvuloplasty ballooncatheter. (In contrast, full dilation would be achieved utilizingdilation of 20 mm or more.) Overtube or trocar 150 is advanced into theascending aorta. Overtube or trocar 150 is pushed beyond aortic valve140 such that the distal end of overtube or trocar 150 is located abovethe highest point of native aortic valve 140. Dilator 154 is removedwhile overtube or trocar 150 remains in place with its distal endlocated above aortic valve 140, as shown in FIG. 5B. It is to beunderstood that the procedure may be modified so that overtube or trocar150 is placed within the left ventricle and remains within the leftventricle throughout the entire implantation procedure. Valve prosthesis10 is advanced through the distal end of overtube or trocar 150 intoascending aorta 160 distal to native leaflets 158, as shown in FIG. 5C.Typically, to facilitate this advancement, prior to the implantationprocedure valve prosthesis 10 is loaded into a delivery tube 202, suchas described hereinbelow with reference to FIGS. 12A-13D. During theimplantation procedure, delivery tube 202 is advanced through overtubeor trocar 150, thereby advancing the valve prosthesis through theovertube or trocar.

FIGS. 6A-B show an implantation of valve prosthesis 10 in ascendingaorta 160, in accordance with an embodiment of the present invention. Asmentioned above with reference to FIGS. 5A-C, the distal end of overtubeor trocar 150 is positioned past native valve leaflets 158. The distalend of valve prosthesis 10 is advanced out of overtube or trocar 150until engagement arms 22 exit overtube or trocar 150 and snap or springopen, as shown in FIG. 6A. Overtube or trocar 150 is gently pulled backuntil engagement arms 22 are brought into aortic sinuses 164. For someapplications, overtube or trocar 150 and/or valve prosthesis 10 aregently rotated as indicated by arrows 166 in order to align engagementarms 22 with respective aortic sinuses 164. Although not typicallynecessary, fluoroscopic, ultrasound, or other surgical imagingtechniques may be used to aid in this positioning. Overtube or trocar150 and valve prosthesis 10 are pulled back slightly, such thatengagement arms 22 are positioned within respective aortic sinuses 164,as shown in FIG. 6B. (Although engagement arms 22 are shown in FIG. 6Bas being in contact with the sinus floors, for some applications theengagement arms do not come in contact with the sinus floors, such asdescribed hereinbelow with reference to FIG. 7B.) Typically, valveprosthesis 10 is configured such that when engagement arms 22 are placedproperly within aortic sinuses 164, outer strut supports 20 are alignedwith commissures 170 (see, for example, FIG. 8A), thus preventing anypossible obstruction of coronary ostia 116 by valve prosthesis 10. Atthis point in the implantation procedure, the distal end of valveprosthesis 10 is free of overtube or trocar 150, and the proximal end ofprosthesis 10 remains in overtube or trocar 150.

For some applications, the use of imaging techniques is not necessary.The careful pulling back of valve prosthesis 10, without application ofexcessive force, generally causes each of engagement arms 22 toautomatically self-align with a respective aortic sinus 164, becauseouter support structure 14, particularly engagement arms 22, generallymatches the three-dimensional shape of aortic valve 140. If one ofengagement arms 22 comes in contact with a commissure 170 during thecareful pulling back of the prosthesis, the arm slides down the slope ofthe leaflet into the aortic sinus. Typically, arms 22 are evenlydistributed around valve prosthesis 10 with a separation of 120 degreesbetween arms, such that all three arms naturally fall into place inrespective sinuses upon even just one of the engagement arms achievingproper alignment with a sinus. This natural alignment generally occurseven if the sinuses themselves are not perfectly distributed at 120degrees from one another.

This alignment process generally ensures positioning of the prostheticleaflets within the aortic sinuses, thus exposing the prostheticleaflets to natural blood vortex formation in the aortic sinuses, whichcontributes to early closure of the prosthetic leaflets, thus reducingclosing volume (i.e., leakage through the prosthetic leaflets beforefully closing), as well as promoting low-impact closure of theprosthetic leaflets, which typically reduces leaflet wear.

For some applications, a correct rotational disposition of theprosthesis with respect to the aortic valve site is determined by thesurgeon based on tactile feedback.

Reference is now made to FIGS. 7A-E, which illustrate valve prosthesis10 in situ upon completion of the implantation procedure, in accordancewith respective embodiments of the present invention. After valveprosthesis 10 is placed properly within native stenosed valve 140, asdescribed hereinabove with reference to FIGS. 5A-6B, the proximal end ofvalve prosthesis 10 is released from overtube or trocar 150, bywithdrawing overtube or trocar 150. Proximal skirt 32 snaps or springsopen to at least partially engage, with its proximal portion 34, theleft-ventricular side of native valve 140, including at least a portionof an inner surface of an LVOT 180. As a result, valve prosthesis 10forms an axial engagement system above and below native valve annulus182 of native valve 140, which axially sandwiches a native valve complex(as defined hereinbelow with reference to FIG. 15) from the aortic andleft-ventricular sides thereof. Native valve leaflets 158 are capturedbetween proximal skirt 32 and engagement arms 22, typically withoutapplying force along the longitudinal axis of the leaflets, in order toavoid shortening of the length of the leaflets, or forced bending,crimping, or folding over of the leaflets. For some applications, barbs120, if provided, pierce aortic annulus 182 on the left-ventricular sideof native valve 140, while for other applications, the barbs are blunt,in which case they generally protrude into the tissue of the aorticannulus, without piercing the tissue. For some applications, supportstructure 14 is configured to elevate native valve leaflets 158 fromwithin the aortic sinuses.

In the embodiment shown in FIG. 7A, upon the completion of theimplantation of prosthesis 10, engagement arms 22 are positioned withinaortic sinuses 164, such that the ends of the engagement arms touch thefloors of the sinuses. Although the ends of the engagement arms areshown touching approximately the radial center of the floors of thesinuses, for some applications, the ends of the engagement arms touchthe floors further from leaflets 158 or closer to the leaflets, or touchthe body of the leaflets, the roots of the leaflets, or the transitionbetween the sinuses and the leaflet roots. Alternatively, the engagementarms are shorter, such as shown in FIG. 7B, such that they do not reachthe floors of the sinuses. Further alternatively, for some applicationsprosthesis 10 does not comprise arms 22, as shown in FIG. 7C.

In the embodiment shown in FIG. 7D, prosthesis 10 has been implantedafter the native valve leaflets have been excised, in accordance with anembodiment of the present invention.

The embodiment illustrated in FIG. 7E shows valve prosthesis 10 in situhaving the configuration of Outer support structure 14 describedhereinabove with reference to FIG. 3F.

For some applications, barbs 120 are coated or otherwise provided with asurface property for enhancing their attachment to tissue of aorticannulus 182. Graft covering 106 of proximal skirt 32 also helps preventregurgitation and device migration.

For some applications, the positioning of arms 22 prior to the openingof proximal skirt 32 prevents native valve leaflets 158 from openingmore than a predetermined desired amount. The support provided by arms22 to the valve leaflets limits the subsequent opening of the leafletsby the proximal skirt. The desired amount of opening is determined atleast in part by the angle between arms 22 and a central longitudinalaxis of the prosthesis (shown, for example, as angle θ in FIG. 7A).Typically, the angle is between about 1 and about 89 degrees, such asbetween about 10 and about 60 degrees, such as 25 degrees, or betweenabout 25 and about 65 degrees. Typically, the angle is predetermined.For some applications, the fixation members of prosthesis 10 areconfigured to prevent opening of the native leaflets to their maximumdiameter.

Reference is again made to FIG. 7A. For some applications, prostheticdistal valve 104 is coupled to strut supports 20 and/or inner struts 30of prosthesis 10 (see, for example, FIG. 1), such that at least 50% ofan axial length of the prosthetic leaflets is distal to native valveleaflets 158. In other words, if prosthetic distal valve 104 has anaxial length L1, a portion L2 of length L1 that is distal to leaflets158 is greater than a portion L3 of length L1 that is proximal toleaflets 158.

FIG. 8A shows valve prosthesis 10 in situ upon completion of theimplantation procedure, as viewed from ascending aorta 160, uponplacement of engagement arms 22 within respective aortic sinuses 164, inaccordance with an embodiment of the present invention. In thisembodiment, engagement arms 22 are positioned within aortic sinuses 154,such that the ends of the engagement arms touch the floors of thesinuses, for example as described hereinabove with reference to FIG. 7A.

FIG. 8B shows valve prosthesis 10 in situ upon completion of theimplantation procedure, in accordance with an embodiment of the presentinvention. In this embodiment, junctures 24 between pairs of engagementanus 22 ride above respective native commissures 170, without impingingon the commissures (i.e., touching or pushing the commissures). In otherwords, there is a gap between each of junctures 24 and its respectivenative commissure 170. Engagement arms 22 are positioned within aorticsinuses 164, such that the ends of the engagement arms touch the floorsof the Sinuses. In this embodiment, the number of engagement arms 22 istypically equal to the number of aortic sinuses 164 of the native valve,and the engagement arms are, radially separated by approximately equalangles. The three-dimensional shape of engagement arms 22 causes theends of the engagement arms to find the lowest point of reach within thefloors of the sinuses, thereby enabling self-alignment of prosthesis 10with the native aortic valve site and commissures 170.

A length L (parallel to a longitudinal axis of prosthesis 10) between(a) each juncture 24 and (b) the contact point of respective engagementarm 22 to the sinus floor is typically greater than about 6 mm, e.g.,greater than about 10 mm, or than about 13 mm. For some applications,length L is between about 10 and about 18 mm, e.g., about 13 mm.

In typical human subjects, the native valve complex has three nativecommissures 170, which define respective commissural high points, andthree respective sinus low points. Prosthesis 10 is configured to matchthese high and low points. Such matching enables axial anchoring,without forced bending, crimping, or folding over of the leaflets, andwithout impinging on the commissures. In this way, prosthesis 10embraces the leaflets, rather than squeezing them.

For some applications, engagement arms 22 are generally aligned with thenative leaflets, thereby avoiding local deformation, and distributingforce over a larger contiguous area of the leaflet surface.

FIG. 8C shows valve prosthesis 10 in situ upon completion of theimplantation procedure, in accordance with an embodiment of the presentinvention. In this embodiment, junctures 24 between pairs of engagementarms 22 ride above respective native commissures 170, impinging on thecommissures (i.e., touching or pushing the commissures). Engagement arms22 are positioned within aortic sinuses 164, such that the ends of theengagement arms do not reach the floors of the sinuses (such asdescribed hereinabove with reference to FIG. 7B). The three-dimensionalshape of junctures 24 causes the junctures to align with commissures170, thereby enabling self-alignment of prosthesis 10 with the nativeaortic valve site and commissures 170. In an embodiment (not shown),junctures 24 apply axial force to (i.e., push) the commissures, andengagement arms 22 apply axial force to aortic sinuses 164.

Reference is made to FIGS. 9A-G, which schematically illustrate aretrograde transaortic approach for implanting valve prosthesis 10, inaccordance with an embodiment of the present invention. Prior to theimplantation procedure, prosthesis 10 is positioned in a retrogradedelivery catheter 250, as shown in FIG. 9G. A retrograde deliverycatheter tube 251 of catheter 250 holds engagement arms 22, and adelivery catheter cap 252 holds proximal skirt 32.

The implantation procedure begins with the transaortic insertion of aguidewire 190 into left ventricle 157, as shown in FIG. 9A. Optionally,stenotic aortic valve 140 is partially dilated to about 15-20 mm (e.g.,about 16 mm), typically using a standard valvuloplasty balloon catheter.(In contrast, full dilation would be achieved by using a ballooncatheter with a diameter of 20 mm or more.) Retrograde delivery catheter250 is advanced over guidewire 190 into ascending aorta 160 towardsnative aortic valve 140, as shown in FIG. 9A. As shown in FIG. 9B,retrograde delivery catheter 250 is advanced over guidewire 190 untildelivery catheter cap 252 passes through native aortic valve 140partially into left ventricle 157. As also shown in FIG. 9B, retrogradedelivery catheter tube 251 is pulled back (in the direction indicated byan arrow 255), while a device stopper 254 (shown in FIG. 90) preventsvalve prosthesis 10 within tube 251 from being pulled back with tube251, so that engagement arms 22 are released and flare out laterallyinto the sinuses. At this stage of the implantation procedure, proximalskirt 32 of prosthesis 10 remains in delivery catheter cap 252.

As shown in FIG. 9 c, at the next step of the implantation procedure,delivery catheter cap 252 is pushed in the direction of the apex of theheart (as shown by an arrow 257), using a retrograde delivery cathetercap shaft 253 that passes through tube 251 and prosthesis 10. Thisadvancing of cap 252 frees proximal skirt 32 to snap or spring open, andengage the inner surface of LVOT 180, Barbs 120, if provided, pierce orprotrude into the aortic annulus on the left-ventricular side of thenative valve. Retrograde delivery catheter tube 251 is further pulledback until the rest of valve prosthesis 10 is released from the tube, asshown in FIG. 9D.

Retrograde delivery catheter tube 251 is again advanced over shaft 253toward the apex of the heart, until tube 251 rejoins cap 252, as shownin FIG. 9E. Retrograde delivery catheter 250 and guidewire 190 arewithdrawn from left ventricle 157, and then from ascending aorta 160,leaving prosthesis 10 in place, as shown in FIG. 9F.

FIGS. 10A and 10B show valve prosthesis 10 in open (systolic) and closed(diastolic) positions, respectively, in accordance with an embodiment ofthe present invention. For clarity of illustration, the surroundinganatomy is not shown in the figure. Collapsible pliant material 105 ofvalve 104 opens during systole and closes during diastole, because ofthe fluid forces applied thereto by the blood flow and the pressuredifference between the left ventricle and the aorta. Alternatively,valve 104 comprises one or more rigid components, such as rigidleaflets, for example as described in U.S. Pat. No. 6,312,465 to Griffinet al. or U.S. Pat. No. 5,908,451 to Yeo, both of which are incorporatedherein by reference. Although prosthesis 10, including valve 104, isshown in the figures as defining a single flow field therethrough, forsome applications the prosthesis and valve are configured so as todefine a plurality of flow fields therethrough, such as shown in severalfigures of the '451 patent to Yeo (e.g., FIGS. 1-3 thereof).

Reference is made to FIGS. 11A-D, which illustrate severalconfigurations for axially coupling valve prosthesis 10 to aorticannulus 182, in accordance with respective embodiments of the presentinvention. For clarity of illustration, these figures show a spread viewof the native valve, viewed from a central axis of the native valve,with native aortic valve leaflets 158 cut longitudinally and pulled tothe sides.

In the configuration shown in FIG. 11A, proximal skirt 32 of valveprosthesis 10 is shaped so as to define a single barb 120 for eachleaflet 158, such that the barbs are generally centered with respect tothe leaflets and engagement arms 22. In the configuration shown in FIG.11B, the proximal skirt is shaped so as to define a pair of barbs 120for each leaflet 158.

In the configuration shown in FIG. 11C, each engagement arm 22 comprisesat least one proximal spike 192, which typically protrudes from a mostproximal region of the engagement arm (i.e., the portion of theengagement arm closest to the apex of the heart). Spikes 192 penetrateaortic annulus 182 from the aortic side, until the spikes exit theannulus on the left-ventricular side, and engage respective barbs 120 onthe left-ventricular side.

In the configuration shown in FIG. 11D, barbs 120 penetrate aorticannulus 182 from the left-ventricular side thereof, until the barbs exitthe annulus on the aortic side, and are coupled to respective engagementarms 22 in respective sinuses. For example, the ends of the barbs may beshaped as hooks, in order to hook around proximal regions of engagementarms 22.

Reference is made to FIGS. 12A-G, which illustrate a holding device 200for holding valve prosthesis 10 prior to the implantation of theprosthesis, in accordance with an embodiment of the present invention.Valve prosthesis 10 is loaded into delivery tube 202 from holding device200, as is described hereinbelow with reference to FIGS. 13A-D. Duringan implantation procedure, delivery tube 202 is advanced into anovertube or trocar, such as overtube or trocar 150, describedhereinabove with reference to FIGS. 5A-C.

FIGS. 12A and 12B illustrate outer and sectional views, respectively, ofholding device 200, in accordance with an embodiment of the presentinvention. For some applications, holding device 200 is shaped so as todefine a conical portion 204 and a tubular portion 206. Holding device200 comprises, for example, plastic.

FIG. 12C shows valve prosthesis 10 loaded in holding device 200, inaccordance with an embodiment of the present invention. The proximal endof valve prosthesis 10 is typically fully compressed within tubularportion 206, while collapsible pliant material 105 is in at least apartially open position within conical portion 204, so as not to deformthe typically delicate material of the valve. The proximal end of theprosthesis is optionally coupled to a device holder 208.

FIGS. 12D and 12E show a configuration of device holder 208, inaccordance with an embodiment of the present invention. In thisconfiguration, device holder 208 is shaped so as to define one or morefemale coupling openings 209, to which corresponding male couplingmembers 218 of valve prosthesis 10 are releasably coupled. For example,proximal portion 34 of proximal skirt 32 (FIGS. 1 and 2B) may be shapedso as to define male coupling members 218. (For clarity of illustration,proximal skirt 32 is not shown in FIG. 12E.) For some applications, thegenders of the coupling elements are reversed.

FIG. 12F illustrates holding device 200 in storage in a jar 210containing a preservation fluid 212 such as glutaraldehyde solution. Forsome applications, holding device 200 is held upright by a holder 214.The contents of the holding device 200 are typically kept inpreservation fluid 212 at all times, and jar 210 is sealed by a cover216.

FIG. 12G illustrates the removal of holding device 200 from storage jar210 prior to loading valve prosthesis 10 into delivery tube 202, inaccordance with an embodiment of the present invention. Holding device200 and its contents are typically washed prior to loading.

Reference is now made to FIGS. 13A-D, which illustrate the loading ofvalve prosthesis 10 into delivery tube 202 from holding device 200, inaccordance with an embodiment of the present invention. As shown in FIG.13A, a distal end of a central delivery shaft 222 includes a deviceholder connector 220. Device holder connector 220 is removably coupledto device holder 208, which is coupled (e.g., fixed) to valve prosthesis10. For example, device holder connector 220 and device holder 208 maycomprise mating, screw-threaded male and female connectors.

As shown in FIG. 13B, retraction, to the right in the figure, of centraldelivery shaft 222 pulls valve prosthesis 10, which is at leastpartially compressed, into delivery tube 202. As shown in FIG. 13, valveprosthesis 10 is pulled into delivery tube 202. Valve prosthesis 10 isplaced in delivery tube 202 such that engagement arms 22 extend fromdelivery tube 202, and thus are free to flare outwards radially, asshown in FIG. 13D. (The engagement arms are constrained from flaringoutwards during the initial steps of an implantation procedure by anovertube or trocar into which delivery tube 202 is inserted, such asovertube or trocar 150, described hereinabove with reference to FIGS.5A-C.)

Although valve prosthesis 10 has been generally described herein asbeing implantable in an aortic valve, in some embodiments of the presentinvention the valve prosthesis is configured to be placed in anothercardiac valve, such as a mitral valve, tricuspid valve, or pulmonaryvalve (such as described hereinbelow with reference to FIG. 14), or in avenous valve. As used herein, including in the claims, “proximal” and“upstream” mean the side of the native or prosthetic valve closer toincoming blood flow, and “distal” and “downstream” mean the side of thenative or prosthetic valve closer to outgoing blood flow.

Reference is made to FIG. 14, which is a schematic illustration of afully-assembled valve prosthesis 300 placed in a pulmonary valve 310, inaccordance with an embodiment of the present invention. Valve prosthesis300 is generally similar to valve prosthesis 10, described herein withreference to FIGS. 1-13D and 16A-17, with appropriate modifications,such as size, for placement in pulmonary valve 310. Valve prosthesis 300comprises two portions that are configured to axially sandwich thenative pulmonary valve complex from right-ventricular 312 and pulmonarytrunk 314 sides thereof.

Reference is made to FIG. 15, which is a schematic anatomicalillustration showing the location of a native valve complex, inaccordance with an embodiment of the present invention. As used herein,including in the claims, the “native valve complex” includes the areademarcated by a box 320, which includes native aortic valve leaflets158, native valve annulus 182, subvalvular tissue 322 on theleft-ventricular side, and the lower half of the aortic, sinuses 164(i.e., up to the top of box 320).

Reference is made to FIGS. 16A-H, which schematically illustrate anothertransapical technique for implanting valve prosthesis 10 (in addition tothe transapical approach described hereinabove with reference to FIGS.5A-8A), in accordance with an embodiment of the present invention. Priorto the implantation procedure, prosthesis 10 is positioned in atransapical delivery catheter 350, as shown in FIG. 16H. A transapicaldelivery tube 351 of catheter 350 holds proximal skirt 32, and atransapical delivery cap 352 holds the distal end of the valve.

The implantation procedure begins with insertion of catheter 350 throughan apex of the heart, into left ventricle 157. For example, the apex maybe punctured using a standard Seldinger technique. A guidewire 390 isadvanced through catheter 350 into ascending aorta 160, as shown in FIG.16A. Optionally, aortic valve 140 is partially dilated to about 15-20 mm(e.g., about 16 mm), typically using a standard valvuloplasty ballooncatheter.

Catheter 350 is advanced over guidewire 390 through native aortic valve140, into ascending aorta 160. Delivery cap 352 is advanced further intothe ascending aorta, by pushing with delivery cap shaft 353. Theadvancement of the delivery cap releases engagement arms 22, which flareout laterally, as shown in FIG. 16B. Catheter 350 is withdrawn towardsthe ventricle, thereby positioning engagement arms 22 in the sinuses, asshown in. FIG. 16C. (Although engagement arms 22 are shown in FIG. 16Cas being in contact with the sinus floors, for some applications theengagement arms do not come in contact with the sinus floors, such asdescribed hereinabove with reference to FIG. 7B.) At this stage of theimplantation procedure, proximal skirt 32 remains in tube 351.

Alternatively, catheter 350 is placed within an overtube (not shown),similar to overtube or trocar 150 (FIGS. 5A-6B), and in such aconfiguration the engagement arms may be released either by pulling backof the overtube, or by the pushing forward of delivery end cap 352.

At the next step of the implantation procedure, tube 351 is withdrawn inthe direction of the apex of the heart. Delivery cap shaft 353 preventscap 352 from being withdrawn with tube 351 (FIG. 16H). As a result,proximal skirt 32 is freed from tube 351 to snap or spring open, andengage the inner surface of LVOT 180. Barbs 120, if provided, pierce orprotrude into the aortic annulus on the left-ventricular side of thenative valve. It is noted that cap 352 remains in place until afterproximal skirt 32 opens. Blood flow thus cannot wash the skirtdownstream during the implantation procedure.

Cap 352 is advanced further into the ascending aorta by pushing ondelivery cap shaft 353, thereby releasing the rest of valve prosthesis10 from cap 352, as shown in FIG. 16E. Delivery tube 351 is advancedover shaft 353 through aortic valve 140, until tube 351 rejoins cap 352,as shown in FIG. 16F. Delivery catheter 350 is withdrawn into the leftventricle, as shown in FIG. 16G, and then from the heart, along withguidewire 390. Prosthesis 10 is left in place, completing theimplantation 10 procedure.

Reference is made to FIG. 17, which is a schematic illustration showinga shape of engagement arms 22, in accordance with an embodiment of thepresent invention. In the figure, outer support structure 14 is shownplaced on an abstract geometric form 400 for clarity of illustration ofthe shape of the structure. As can be seen, in this embodimentengagement arms 22 have a shape that is generally upwardly concave(except at the junctures), i.e., concave in a downstream direction. Inmathematical terms, this shape can be characterized by the functionz″(r)>0, where z is the height at any given point on one of engagementarms 22 (e.g., point P), and r is the distance from the z-axis to thegiven point. (It is understood that the arms may be shaped so as toinclude one or more relatively short sections that are upwardly convex(i.e., z″(r)<0), but that the general shape of the arms is upwardlyconcave.)

For some applications, engagement arms 22 are shaped such that at leasta portion of the arms is parallel to the longitudinal axis of outersupport structure 14.

In en embodiment, the shape of the arms is characterized by the functionz″(r)<=0, i.e., the general shapes of the arms is not upwardly concave.

As used herein, including in the claims, the “ascending aorta” includesthe aortic root (sinuses) and the tubular portion above the root.

Although valve prostheses 10 and 300 have been described herein ascomprising a valve, for some applications the prostheses do not comprisevalves.

The scope of the present invention includes embodiments described in thefollowing applications, which are assigned to the assignee of thepresent application and are incorporated herein by reference. In anembodiment, techniques and apparatus described in one or more of thefollowing applications are combined with techniques and apparatusdescribed herein:

-   -   U.S. patent application Ser. No. 11/024,908, filed Dec. 30,        2004, entitled, “Fluid flow prosthetic device,” which published        as US Patent Application Publication 2006/0149360;    -   International Patent Application PCT/IL2005/001399, filed Dec.        29, 2005, entitled, “Fluid flow prosthetic device,” which        published as PCT Publication WO 06/070372; and/or    -   International Patent Application PCT/IL2004/000601, filed Jul.        6, 2004, entitled, “Implantable prosthetic devices particularly        for transarterial delivery in the treatment of aortic stenosis,        and methods of implanting such devices,” which published as PCT        Publication WO 05/002466, and U.S. patent application Ser. No.        10/563,384, filed Apr. 20, 2006, in the national stage thereof,        which published as US Patent Application Publication        2006/0259134.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present inventionincludes both combinations and subcombinations of the various featuresdescribed hereinabove, as well as variations and modifications thereofthat are not in the prior art, which would occur to persons skilled inthe art upon reading the foregoing description.

1. Apparatus comprising a prosthesis for implantation at a nativesemilunar valve of a native valve complex of a subject, the native valvecomplex having semilunar sinuses and native commissures, the prosthesiscomprising: a distal fixation member, configured to be positioned in adownstream artery of the subject selected from the group consisting of:an ascending aorta, and a pulmonary trunk, and shaped so as to defineexactly three proximal engagement arms that are configured to bepositioned at least partially within respective ones of the semilunarsinuses, and, in combination, to apply, to tissue that defines thesemilunar sinuses, a first axial force directed toward a ventricle ofthe subject; and a proximal fixation member coupled to the distalfixation member, the proximal fixation member configured to bepositioned at least partially on a ventricular side of the nativesemilunar valve, and to apply, to the ventricular side of the nativevalve complex, a second axial force directed toward the downstreamartery, such that application of the first and second forces couples theprosthesis to the native valve complex.
 2. The apparatus according toclaim 1, wherein the native semilunar valve includes a native aorticvalve, wherein the downstream artery includes the ascending aorta,wherein the semilunar sinuses include respective aortic sinuses, whereinthe distal fixation member is configured to be positioned in theascending aorta, and wherein the proximal engagement arms are configuredto be positioned at least partially within the respective aorticsinuses.
 3. The apparatus according to claim 1, wherein the nativesemilunar valve includes a native pulmonary valve, wherein thedownstream artery includes the pulmonary trunk, wherein the semilunarsinuses include respective pulmonary sinuses, wherein the distalfixation member is configured to be positioned in the pulmonary trunk,and wherein the proximal engagement arms are configured to be positionedat least partially within the respective pulmonary sinuses.
 4. Theapparatus according to claim 1, wherein the distal and proximal fixationmembers are configured to couple the prosthesis to the native valvecomplex by axially sandwiching the native valve complex from adownstream side and the ventricular side thereof, upon implantation ofthe prosthesis.
 5. The apparatus according to claim 1, wherein thedistal fixation member does not press upon the native commissures uponimplantation of the prosthesis.
 6. The apparatus according to claim 1,wherein the prosthesis is configured to apply a radial force of lessthan 0.5 pounds outwardly against the native semilunar valve.
 7. Theapparatus according to claim 1, wherein the prosthesis is configured toapply the first axial force with a force of at least 40 g duringdiastole.
 8. The apparatus according to claim 1, wherein the prosthesisis configured to apply the second axial force with a force of at least 1g during systole.
 9. The apparatus according to claim 1, wherein theprosthesis is configured such that any radial force applied by theprosthesis outwardly against the native semilunar valve is insufficientby itself to chronically maintain the prosthesis in position withrespect to the native valve complex under conditions of normal cardiacmotion.
 10. The apparatus according to claim 1, wherein the prosthesisis configured, upon implantation thereof, to embrace, without squeezing,leaflets of the native semilunar valve.
 11. The apparatus according toclaim 1, wherein the distal fixation member is configured to bepositioned in the downstream artery during an implantation procedurebefore the proximal fixation member is positioned at least partially onthe ventricular side of the native valve complex.
 12. The apparatusaccording to claim 1, wherein the distal fixation member is configuredsuch that it does not fold over leaflets of the native semilunar valveupon implantation of the prosthesis.
 13. The apparatus according toclaim 1, wherein the distal fixation member is configured such that itdoes not push leaflets of the native semilunar valve towards semilunarsinus floors of the native valve complex upon implantation of theprosthesis.
 14. The apparatus according to claim 1, wherein each of theproximal engagement arms is shaped so as define at least one trough thatis configured to be positioned at least partially within a respectiveone of the semilunar sinuses.
 15. The apparatus according to claim 1,wherein the three engagement arms meet one another at three respectivejunctures, wherein the engagement arms are shaped so as define threepeak complexes at the three respective junctures, and three troughcomplexes, each of which is between two of the peak complexes, andwherein, upon implantation of the prosthesis, at least a portion of eachof the peak complexes is disposed distal to and in rotational alignmentwith a respective one of the native commissures of the native semilunarvalve, and each of the trough complexes is disposed at least partiallywithin the respective one of the semilunar sinuses.
 16. The apparatusaccording to claim 1, wherein the engagement arms are configured to bepositioned, during an implantation procedure, at least partially withinthe respective ones of the semilunar sinuses before the proximalfixation member is positioned at least partially on the ventricular sideof the native valve complex, such that the engagement arms preventleaflets of the native valve complex from opening more than apredetermined desired amount, the opening being because of force appliedby the proximal fixation member to the leaflets.
 17. The apparatusaccording to claim 1, wherein the proximal fixation member, isconfigured to be positioned at least partially in a ventricle of thesubject upon implantation of the prosthesis.
 18. The apparatus accordingto claim 1, wherein the prosthesis is configured to less than fully openleaflets of the native valve complex when the prosthesis is implanted atthe native semilunar valve complex.
 19. The apparatus according to claim1, wherein the distal fixation member is configured to elevate leafletsof the native semilunar valve from within the semilunar sinuses uponimplantation of the prosthesis.
 20. The apparatus according to claim 1,wherein the distal fixation member is configured to apply the firstaxial force to respective roots of one or more leaflets of the nativevalve complex.
 21. The apparatus according to claim 1, wherein thedistal fixation member is configured, to apply the first axial force torespective transitions between respective semilunar sinus floors, andone or more leaflets of the native valve complex.
 22. The apparatusaccording to claim 1, wherein the prosthesis is configured to apply thefirst axial force such that a ratio of (a) the first axial force to (h)a radial force applied outwardly by the prosthesis against the nativesemilunar valve is greater than 1.5:1.
 23. The apparatus according toclaim 22, wherein the prosthesis is configured to apply the first axialforce such that the ratio is greater than 3:1.
 24. The apparatusaccording to claim 23, wherein the prosthesis is configured to apply thefirst axial force such that the ratio is greater than 6:1.
 25. Theapparatus according to claim 1, wherein the prosthesis is configured toapply the second axial force such that a ratio of (a) the second axialforce to (b) a radial force applied outwardly by the prosthesis againstthe native semilunar valve is greater than 1.5:1.
 26. The apparatusaccording to claim 25, wherein the prosthesis is configured to apply thesecond axial force such that the ratio is greater than 3:1.
 27. Theapparatus according to claim 26, wherein the prosthesis is configured toapply the second axial force such that the ratio is greater than 6:1.28. The apparatus according to claim 1, wherein the prosthesis comprisesa prosthetic valve configured to assume a closed position duringdiastole and an open position during systole.
 29. The apparatusaccording to claim 28, wherein the prosthetic valve comprises acollapsible pliant material, configured to assume the open and closedpositions.
 30. The apparatus according to claim 28, wherein the distaland proximal fixation members and the prosthetic valve are configured todefine a single flow field through the distal and proximal fixationmembers and the prosthetic valve.
 31. The apparatus according to claim28, wherein the distal and proximal fixation members and the prostheticvalve are configured to define a plurality of flow fields through thedistal and proximal fixation members and the prosthetic valve.
 32. Theapparatus according to claim 28, wherein the prosthetic valve comprisesone or more prosthetic leaflets, and wherein the prosthetic valve iscoupled to the prosthesis such that at least 50% of an axial length ofthe prosthetic leaflets is distal to native valve leaflets of the nativesemilunar valve upon implantation of the prosthesis.
 33. The apparatusaccording to claim 1, wherein the distal fixation member is configuredto apply the first axial force to one or more semilunar sinus floors ofthe native valve complex.
 34. The apparatus according to claim 33,wherein the distal fixation member is configured not to apply force toleaflets of the native semilunar valve.
 35. The apparatus according toclaim 1, wherein the proximal fixation member is shaped so as to defineat least one barb configured to apply a barb force to the ventricularside of the native valve complex.
 36. The apparatus according to claim35, wherein the at least one barb is configured to pierce theventricular side of the native valve complex.
 37. The apparatusaccording to claim 35, wherein the at least one barb is configured toprotrude into tissue of the ventricular side of the native valuecomplex, without piercing the tissue.
 38. The apparatus according toclaim 35, wherein the distal fixation member is shaped so as to defineat least one mating barb, and wherein the at least one barb of theproximal fixation member is configured to engage the at least one matingbarb, so as to help hold the prosthesis in place.
 39. The apparatusaccording to claim 1, wherein the proximal and distal fixation membersare collapsible.
 40. The apparatus according to claim 39, wherein thedistal fixation member is configured to be positioned, during animplantation procedure, in the downstream artery while collapsed, and tobe expanded before the proximal fixation member is positioned at leastpartially on the ventricular side of the native valve complex.
 41. Theapparatus according to claim 39, comprising at least one tube selectedfrom the group consisting of an overtube and a trocar, wherein theproximal and distal fixation members are configured to be stored in theselected tube while collapsed, and to expand upon being deployed fromthe selected tube.
 42. The apparatus according to claim 1, wherein theproximal fixation member comprises an inner support structure, andwherein the distal fixation member comprises an outer support structurethat is placed partially over the inner support structure.
 43. Theapparatus according to claim 42, wherein the outer support structure isshaped so as to define exactly three distal diverging strut supports,from which respective ones of the proximal engagement arms extendradially outward.
 44. The apparatus according to claim 43, wherein theprosthesis is configured such that, upon implantation at the nativevalve complex, the engagement arms are aligned by rotation withrespective ones of the semilunar sinuses.
 45. The apparatus according toclaim 44, wherein the prosthesis is configured such that, uponimplantation at the native valve complex, the strut supports are alignedwith respective ones of the native commissures.
 46. The apparatusaccording to claim 43, wherein the prosthesis is configured such that,upon implantation at the native valve complex, the engagement arms arealigned by rotation with respective ones of the semilunar sinuses, andwherein the prosthesis is configured such that the engagement armsself-align themselves by rotation during implantation of the prosthesisat the native valve complex.
 47. The apparatus according to claim 42,wherein the inner support structure is shaped so as to define aplurality of distal diverging inner struts.
 48. The apparatus accordingto claim 42, wherein the inner support structure is shaped so as todefine a bulging proximal skirt, a proximal portion of which isconfigured to apply the second axial force.
 49. The apparatus accordingto claim 48, wherein the prosthesis comprises a graft covering thatcovers at least a portion of the skirt.
 50. The apparatus according toclaim 48, wherein the inner support structure is shaped so as to definea plurality of distal diverging inner struts, and wherein the skirtextends from the inner struts.
 51. The apparatus according to claim 50,wherein the outer support structure is shaped so as to define exactlythree distal diverging strut supports, from which respective ones of theproximal engagement arms extend radially outward, and wherein each ofthe strut supports is positioned over a respective one of the innerstruts.
 52. The apparatus according to claim 51, wherein the engagementarms are positioned over a portion of the skirt.
 53. The apparatusaccording to claim 51, wherein the prosthesis comprises a valvecomprising a collapsible pliant material, configured to assume a closedposition during diastole and an open position during systole, whereinthe pliant material comprises a plurality of segments, at least two ofwhich are coupled together by one of the strut supports and itsrespective one of the inner struts.
 54. Apparatus comprising aprosthesis for implantation at a native semilunar valve of a nativevalve complex of a subject, the prosthesis comprising: a distal fixationmember, configured to be positioned in a downstream artery of thesubject selected from the group consisting of: an ascending aorta, and apulmonary trunk, and to apply, to tissue that defines one or moresemilunar sinuses of the native valve complex, a first axial forcedirected toward a ventricle of the subject; and a proximal fixationmember coupled to the distal fixation member, the proximal fixationmember configured to be positioned at least partially on a ventricularside of the native semilunar valve, and to apply, to the ventricularside of the native valve complex, a second axial force directed towardthe downstream artery, such that application of the first and secondforces couples the prosthesis to the native valve complex.
 55. Theapparatus according to claim 54, wherein the native semilunar valveincludes a native aortic valve, wherein the downstream artery includesthe ascending aorta, wherein the semilunar sinuses include respectiveaortic sinuses, and wherein the distal fixation member is configured tobe positioned in the ascending aorta, and to apply the first axial forceto the tissue that defines the one or more aortic sinuses.
 56. Theapparatus according to claim 54, wherein the native semilunar valveincludes a native pulmonary valve, wherein the downstream arteryincludes the pulmonary trunk, wherein semilunar sinuses includerespective pulmonary sinuses, and wherein the distal fixation member isconfigured to be positioned in the pulmonary trunk, and to apply thefirst axial force to the tissue that defines the one or more pulmonarysinuses.
 57. The apparatus according to claim 54, wherein the distal andproximal fixation members are configured to couple the prosthesis to thenative valve complex by axially sandwiching the native valve complexfrom a downstream side and the ventricular side thereof, uponimplantation of the prosthesis.
 58. The apparatus according to claim 54,wherein the distal fixation member does not press upon native valvecommissures of the native semilunar valve upon implantation of theprosthesis.
 59. The apparatus according to claim 54, wherein theprosthesis is configured to apply a radial force of less than 0.5 poundsoutwardly against the native semilunar valve.
 60. The apparatusaccording to claim 54, wherein the prosthesis is configured to apply thefirst axial force with a force of at least 40 g during diastole.
 61. Theapparatus according to claim 54, wherein the prosthesis is configured toapply the second axial force with a force of at least 1 g duringsystole.
 62. The apparatus according to claim 54, wherein the prosthesisis configured such that any radial force applied by the prosthesisoutwardly against the native semilunar valve is insufficient by itselfto chronically maintain the prosthesis in position with respect to thenative valve complex under conditions of normal cardiac motion.
 63. Theapparatus according to claim 54, wherein the prosthesis is configured,upon implantation thereof, to embrace, without squeezing, leaflets ofthe native semilunar valve.
 64. The apparatus according to claim 54,wherein the distal fixation member is configured to be positioned in thedownstream artery during an implantation procedure before the proximalfixation member is positioned at least partially on the ventricular sideof the native valve complex.
 65. The apparatus according to claim 54,wherein the distal fixation member is configured such that it does notfold over leaflets of the native semilunar valve upon implantation ofthe prosthesis.
 66. The apparatus according to claim 54, wherein thedistal fixation member is configured such that it does not push leafletsof the native semilunar valve towards semilunar sinus floors of thenative valve complex upon implantation of the prosthesis.
 67. Theapparatus according to claim 54, wherein the prosthesis is configured toless than fully open leaflets of the native valve complex when theprosthesis is implanted at the native valve complex.
 68. The apparatusaccording to claim 54, wherein the distal fixation member is configuredto apply the first axial force to respective roots of one or moreleaflets of the native valve complex.
 69. The apparatus according toclaim 54, wherein the distal fixation member is configured to apply thefirst axial force to respective transitions between respective semilunarsinus floors and one or more leaflets of the native valve complex. 70.The apparatus according to claim 54, wherein the proximal fixationmember is configured to be positioned at least partially in a ventricleof the subject upon implantation of the prosthesis.
 71. The apparatusaccording to claim 54, wherein the prosthesis is configured to apply thefirst axial force such that a ratio of (a) the first axial force to (b)a radial force applied outwardly by the prosthesis against the nativesemilunar valve is greater than 1.5:1.
 72. The apparatus according toclaim 71, wherein the prosthesis is configured, to apply the first axialforce such that the ratio is greater than 3:1.
 73. The apparatusaccording to claim 72, wherein the prosthesis is configured to apply thefirst axial force such that the ratio is greater than 6:1.
 74. Theapparatus according to claim 54, wherein the prosthesis is configured toapply the second axial force such that a ratio of (a) the second axialforce to (b) a radial force applied outwardly by the prosthesis againstthe native semilunar valve is greater than 1.5:1.
 75. The apparatusaccording to claim 74, wherein the prosthesis is configured to apply thesecond axial force such that the ratio is greater than 3:1.
 76. Theapparatus according to claim 75, wherein the prosthesis is configured toapply the second axial force such that the ratio is greater than 6:1.77. The apparatus according to claim 54, wherein the prosthesiscomprises a prosthetic valve configured to assume a closed positionduring diastole and an open position during systole.
 78. The apparatusaccording to claim 77, wherein the prosthetic valve comprises acollapsible pliant material, configured to assume the open and closedpositions.
 79. The apparatus according to claim 77, wherein the distaland proximal fixation members and the prosthetic valve are configured todefine a single flow field through the distal and proximal fixationmembers and the prosthetic valve.
 80. The apparatus according to claim77, wherein the distal and proximal fixation members and the prostheticvalve are configured to define a plurality of flow fields through thedistal and proximal fixation members and the prosthetic valve.
 81. Theapparatus according to claim 77, wherein the prosthetic valve comprisesone or more prosthetic leaflets, and wherein the prosthetic valve iscoupled to the prosthesis such that at least 50% of an axial length ofthe prosthetic leaflets is distal to native valve leaflets of the nativesemilunar valve upon implantation of the prosthesis.
 82. The apparatusaccording to claim 54, wherein the distal fixation member is configuredto apply the first axial force to one or more semilunar sinus floors ofthe native valve complex.
 83. The apparatus according to claim 82,wherein the distal fixation member is configured not to apply force toleaflets of the native semilunar valve.
 84. The apparatus according toclaim 54, wherein the distal fixation member is shaped so as to defineone or more proximal engagement arms that are configured to bepositioned at least partially within respective ones of the semilunarsinuses, and, in combination, to apply the first axial force.
 85. Theapparatus according to claim 84, wherein the distal fixation member isshaped so as to define exactly three proximal engagement arms.
 86. Theapparatus according to claim 85, wherein each of the proximal engagementarms is shaped so as define at least one trough that is configured to bepositioned at least partially within a respective one of the semilunarsinuses.
 87. The apparatus according to claim 85, wherein the threeengagement arms meet one another at three respective junctures, whereinthe engagement arms are shaped so as define three peak complexes at thethree respective junctures, and three trough complexes, each of which isbetween two of the peak complexes, and wherein, upon implantation of theprosthesis, at least a portion of each of the peaks is disposed distalto and in rotational alignment with a respective native commissure ofthe native semilunar valve, and each of the trough complexes is disposedat least partially within the respective one of the semilunar sinuses.88. The apparatus according to claim 84, wherein the distal fixationmember is shaped so as to define exactly two proximal engagement arms.89. The apparatus according to claim 84, wherein the engagement arms areconfigured to be positioned, during an implantation procedure, at leastpartially within the respective ones of the semilunar sinuses before theproximal fixation member is positioned at least partially on theventricular side of the native valve complex, such that the engagementarms prevent leaflets of the native valve complex from opening more thana predetermined desired amount, the opening being because of forceapplied by the proximal fixation member to the leaflets.
 90. Theapparatus according to claim 54, wherein the proximal fixation member isshaped so as to define at least one barb configured to apply a barbforce to the ventricular side of the native valve complex.
 91. Theapparatus according to claim 90, wherein the at least one barb isconfigured to pierce the ventricular side of the native valve complex.92. The apparatus according to claim 90, wherein the at least one barbis configured to protrude into tissue of the ventricular side of thenative value complex, without piercing the tissue.
 93. The apparatusaccording to claim 90, wherein the distal fixation member is shaped soas to define at least one mating barb, and wherein the at least one barbof the proximal fixation member is configured to engage the at least onemating barb, so as to help hold the prosthesis in place.
 94. Theapparatus according to claim 54, wherein the proximal and distalfixation members are collapsible.
 95. The apparatus according to claim94, wherein the distal fixation member is configured to be positioned,during an implantation procedure, in the downstream artery whilecollapsed, and to be expanded before the proximal fixation member ispositioned at least partially on the ventricular side of the nativevalve complex.
 96. The apparatus according to claim 94, comprising atleast one tube selected from the group consisting of an overtube and atrocar, wherein the proximal and distal fixation members are configuredto be stored in the selected tube while collapsed, and to expand uponbeing deployed from the selected tube.
 97. The apparatus according toclaim 54, wherein the proximal fixation member comprises an innersupport structure, and wherein the distal fixation member comprises anouter support structure that is placed partially over the inner supportstructure.
 98. The apparatus according to claim 97, wherein the outersupport structure is shaped so as to define a plurality of distaldiverging strut supports, from which a plurality of proximal engagementarms extend radially outward.
 99. The apparatus according to claim 98,wherein the prosthesis is configured such that, upon implantation at thenative valve complex, the engagement arms are aligned by rotation withrespective ones of the semilunar sinuses.
 100. The apparatus accordingto claim 99, wherein the prosthesis is configured such that, uponimplantation at the native valve complex, the strut supports are alignedwith respective commissures of the native valve complex.
 101. Theapparatus according to claim 99, wherein the prosthesis is configuredsuch that the engagement arms self-align themselves by rotation duringimplantation of the prosthesis at the native valve complex.
 102. Theapparatus according to claim 97, wherein the inner support structure isshaped so as to define a plurality of distal diverging inner struts.103. The apparatus according to claim 97, wherein the inner supportstructure is shaped so as to define a bulging proximal skirt, a proximalportion of which is configured to apply the second axial force.
 104. Theapparatus according to claim 103, wherein the prosthesis comprises agraft covering that covers at least a portion of the skirt.
 105. Theapparatus according to claim 103, wherein the inner support structure isshaped so as to define a plurality of distal diverging inner struts, andwherein the skirt extends from the inner struts.
 106. The apparatusaccording to claim 105, wherein the outer support structure is shaped soas to define a plurality of distal diverging strut supports, from whicha plurality of proximal engagement arms extend radially outward, andwherein each of the strut supports is positioned over a respective oneof the inner struts.
 107. The apparatus according to claim 106, whereinthe engagement arms are positioned over a portion of the skirt.
 108. Theapparatus according to claim 106, wherein the prosthesis comprises avalve comprising a collapsible pliant material, configured to assume aclosed position during diastole and an open position during systole, andwherein the pliant material comprises a plurality of segments, at leasttwo of which are coupled together by one of the strut supports and itsrespective one of the inner struts.
 109. Apparatus comprising aprosthesis for implantation at a native semilunar valve of a nativevalve complex of a subject, the prosthesis comprising: a distal fixationmember, configured to be positioned in a downstream artery of thesubject selected from the group consisting of an ascending aorta, and apulmonary trunk, and to apply, to native commissures of the nativesemilunar valve, a first axial force directed toward a ventricle of thesubject, without applying any force to native leaflets of the nativesemilunar valve, and wherein the distal fixation member is configured torotationally align with the native semilunar valve; and a proximalfixation member coupled to the distal fixation member, the proximalfixation member configured to be positioned at least partially on aventricular side of the native valve complex, and to apply a secondaxial force directed toward the downstream artery, such that applicationof the first and second forces couples the prosthesis to the nativevalve complex by axially sandwiching the native valve complex from adownstream side and the ventricular side thereof, upon implantation ofthe prosthesis.
 110. The apparatus according to claim 109, wherein thenative semilunar valve includes a native aortic valve, wherein thedownstream artery includes the ascending aorta and wherein the distalfixation member is configured to be positioned in the ascending aorta,and to apply the first axial force to the native commissures of thenative aortic valve.
 111. The apparatus according to claim 109, whereinthe native semilunar valve includes a native pulmonary valve, whereinthe downstream artery includes the pulmonary trunk, and wherein thedistal fixation member is configured to be positioned in the pulmonarytrunk, and to apply the first axial force to the native commissures ofthe native pulmonary valve.
 112. The apparatus according to claim 109,wherein the distal fixation member is configured to rotationallyself-align with the native semilunar valve.
 113. The apparatus accordingto claim 109, wherein the distal fixation member comprises one or moreengagement arms that are positioned at least partially within respectivesemilunar sinuses of the native valve complex, upon implantation of theprosthesis.
 114. The apparatus according to claim 113, wherein theengagement arms are configured to apply respective forces to respectivefloors of the semilunar sinuses, upon implantation of the prosthesis.115. The apparatus according to claim 113, wherein the engagement armsare configured not to apply any force to floors of the semilunarsinuses, upon implantation of the prosthesis.
 116. Apparatus comprisinga prosthesis for implantation at a native semilunar valve of a nativevalve complex of a subject, the prosthesis comprising: a distal fixationmember, configured to be positioned in a downstream artery of thesubject selected from the group consisting of an ascending aorta, and apulmonary trunk, and to apply a first axial force directed toward aventricle of the subject; and a proximal fixation member coupled to thedistal fixation member, the proximal fixation member configured to bepositioned at least partially on a ventricular side of the native valvecomplex, and to apply a second axial force directed toward thedownstream artery, such that application of the first and second forcescouples the prosthesis to the native valve complex by axiallysandwiching the native valve complex from a downstream side and theventricular side thereof, wherein the prosthesis is configured to applya radial force of less than 0.5 pounds outwardly against the nativesemilunar valve.
 117. The apparatus according to claim 116, wherein thenative semilunar valve includes a native aortic valve, wherein thedownstream artery includes the ascending aorta, and wherein the distalfixation member is configured to be positioned in the ascending aorta.118. The apparatus according to claim 116, wherein the native semilunarvalve includes a native pulmonary valve, wherein the downstream arteryincludes the pulmonary trunk, and wherein the distal fixation member isconfigured to be positioned in the pulmonary trunk.
 119. The apparatusaccording to claim 116, wherein the distal fixation member does notpress upon native valve commissures of the native semilunar valve uponimplantation of the prosthesis.
 120. The apparatus according to claim116, wherein the prosthesis is configured to apply the first axial forcesuch that a ratio of (a) the first axial force to (b) the radial forceis greater than 1.5:1.
 121. The apparatus according to claim 116,wherein the prosthesis is configured to apply the second axial forcesuch that a ratio of (a) the second axial force to (b) the radial forceis greater than 1.5:1.
 122. The apparatus according to claim 116,wherein the prosthesis is configured to apply the first axial force witha force of at least 40 g during diastole.
 123. The apparatus accordingto claim 116, wherein the prosthesis is configured to apply the secondaxial force with a force of at least 1 g during systole.
 124. Theapparatus according to claim 116, wherein the prosthesis is configuredsuch that any radial force applied by the prosthesis outwardly againstthe native semilunar valve is insufficient by itself to chronicallymaintain the prosthesis in position with respect to the native valvecomplex under conditions of normal cardiac motion.
 125. The apparatusaccording to claim 116, wherein the prosthesis is configured, uponimplantation thereof, to embrace, without squeezing, leaflets of thenative semilunar valve.
 126. The apparatus according to claim 116,wherein the distal fixation member is configured such that it does notfold over leaflets of the native semilunar valve upon implantation ofthe prosthesis.
 127. The apparatus according to claim 116, wherein theprosthesis is configured to less than fully open leaflets of the nativevalve complex when the prosthesis is implanted at the native valvecomplex.
 128. The apparatus according to claim 116, wherein the proximalfixation member is configured to be positioned at least partially in aventricle of the subject upon implantation of the prosthesis.
 129. Theapparatus according to claim 116, wherein the prosthesis comprises avalve configured to assume a closed position during diastole and an openposition during systole.
 130. The apparatus according to claim 129,wherein the valve comprises a collapsible pliant material, configured toassume the open and closed positions.
 131. The apparatus according toclaim 129, wherein the distal and proximal fixation members and thevalve are configured to define a single flow field through the distaland proximal fixation members and the valve.
 132. The apparatusaccording to claim 129, wherein the distal and proximal fixation membersand the valve are configured to define a plurality of flow fieldsthrough the distal and proximal fixation members and the valve.
 133. Theapparatus according to claim 129, wherein the valve comprises one ormore prosthetic leaflets, and wherein the valve is coupled to theprosthesis such that at least 50% of an axial length of the prostheticleaflets is distal to native valve leaflets of the native semilunarvalve upon implantation of the prosthesis.
 134. The apparatus accordingto claim 116, wherein the proximal fixation member is shaped so as todefine at least one barb configured to apply a barb force to theventricular side of the native valve complex.
 135. The apparatusaccording to claim 134, wherein the at least one barb is configured topierce the ventricular side of the native valve complex.
 136. Theapparatus according to claim 134, wherein the at least one barb isconfigured to protrude into tissue of the ventricular side of the nativevalve complex, without piercing the tissue.
 137. The apparatus accordingto claim 134, wherein the distal fixation member is shaped so as todefine at least one mating barb, and wherein the at least one barb ofthe proximal fixation member is configured to engage the at least onemating barb, so as to help hold the prosthesis in place.
 138. Theapparatus according to claim 116, wherein the proximal and distalfixation members are collapsible.
 139. The apparatus according to claim138, wherein the distal fixation member is configured to be positioned,during an implantation procedure, in the downstream artery whilecollapsed, and to be expanded before the proximal fixation member ispositioned at least partially on the ventricular side of the nativevalve complex.
 140. The apparatus according to claim 138, comprising atleast one tube selected from the group consisting of: an overtube and atrocar, wherein the proximal and distal fixation members are configuredto be stored in the selected tube while collapsed, and to expand uponbeing deployed from the selected tube.
 141. The apparatus according toclaim 116, wherein the proximal fixation member comprises an innersupport structure, and wherein the distal fixation member comprises anouter support structure that is placed partially over the inner supportstructure.
 142. The apparatus according to claim 141, wherein the outersupport structure is shaped so as to define a plurality of distaldiverging strut supports, from which a plurality of proximal engagementarms extend radially outward.
 143. The apparatus according to claim 141,wherein the inner support structure is shaped so as to define aplurality of distal diverging inner struts.
 144. The apparatus accordingto claim 141, wherein the inner support structure is shaped so as todefine a bulging proximal skirt, a proximal portion of which isconfigured to apply the second axial force.
 145. The apparatus accordingto claim 144, wherein the prosthesis comprises a graft covering thatcovers at least a portion of the skirt.
 146. The apparatus according toclaim 144, wherein the inner support structure is shaped so as to definea plurality of distal diverging inner struts, and wherein the skirtextends from the inner struts.
 147. The apparatus according to claim146, wherein the outer support structure is shaped so as to define aplurality of distal diverging strut supports, from which a plurality ofproximal engagement arms extend radially outward, and wherein each ofthe strut supports is positioned over a respective one of the innerstruts.
 148. The apparatus according to claim 147, wherein theengagement arms are positioned over a portion of the skirt.
 149. Theapparatus according to claim 147, wherein the prosthesis comprises avalve comprising a collapsible pliant material, configured to assume aclosed position during diastole and an open position during systole,wherein the pliant material comprises a plurality of segments, at leasttwo of which are coupled together by one of the strut supports and itsrespective one of the inner struts.
 150. A method for implanting a valveprosthesis at a native semilunar valve of a native valve complex of asubject, the method comprising: providing a distal fixation member ofthe valve prosthesis coupled to a proximal fixation member of the valveprosthesis, which distal fixation member is shaped so as to defineexactly three proximal engagement arms; positioning the distal fixationmember in a downstream artery of the subject selected from the groupconsisting of: an ascending aorta, and a pulmonary trunk, such that thethree proximal engagement arms are positioned at least partially withinrespective semilunar sinuses of the native valve complex, and, incombination, apply, to tissue that defines the semilunar sinuses, afirst axial force directed toward a ventricle of the subject; andpositioning the proximal fixation member at least partially on aventricular side of the native semilunar valve, such that the proximalfixation member applies, to the ventricular side of the native valvecomplex, a second axial force directed toward the downstream artery,such that application of the first and second forces couples theprosthesis to the native valve complex.
 151. The method according toclaim 150, wherein the native semilunar valve includes a native aorticvalve, wherein the downstream artery includes the ascending aorta, andwherein positioning the distal fixation member comprises positioning thedistal fixation member in the ascending aorta.
 152. The method accordingto claim 150, wherein the native semilunar valve includes a nativepulmonary valve, wherein the downstream artery includes the pulmonarytrunk, and wherein positioning the distal fixation member comprisespositioning the distal fixation member in the pulmonary trunk.
 153. Themethod according to claim 150, wherein providing comprises coupling thedistal fixation member to the proximal fixation member beforepositioning the distal fixation member and before positioning theproximal fixation member.
 154. The method according to claim 150,wherein providing comprises coupling the distal fixation member to theproximal fixation member after performing at least one action selectedfrom the group consisting of: positioning the distal fixation member,and positioning the proximal fixation member.
 155. The method accordingto claim 150, wherein the distal fixation member and the proximalfixation member are fabricated as one integrated structure, and whereinproviding the distal fixation member coupled to the proximal fixationmember comprises providing the distal fixation member and the proximalfixation member that are fabricated as one integrated structure. 156.The method according to claim 150, wherein positioning the distal andproximal fixation members comprises positioning the engagement arms atleast partially within the respective ones of the semilunar sinusesbefore positioning the proximal fixation member at least partially onthe ventricular side of the native valve complex, such that theengagement arms prevent leaflets of the native valve complex fromopening more than a predetermined desired amount, the opening beingbecause of force applied by the proximal fixation member to theleaflets.
 157. A method for implanting a valve prosthesis at a nativesemilunar valve of a native valve complex of a subject, the methodcomprising: providing a distal fixation member of the valve prosthesiscoupled to a proximal fixation member of the valve prosthesis;positioning the distal fixation member in a downstream artery of thesubject selected from the group consisting of: an ascending aorta, and apulmonary trunk, such that the distal fixation member applies, to adownstream side of the native valve complex, a first axial forcedirected toward a ventricle of the subject; and positioning the proximalfixation member at least partially on a ventricular side of the nativesemilunar valve, such that the proximal fixation member applies, to aventricular side of the native semilunar valve, a second axial forcedirected toward the downstream artery, such that application of thefirst and second forces couples the prosthesis to the native semilunarvalve.
 158. The method according to claim 157, wherein the nativesemilunar valve includes a native aortic valve, wherein the downstreamartery includes the ascending aorta, and wherein positioning the distalfixation member comprises positioning the distal fixation member in theascending aorta.
 159. The method according to claim 157, wherein thenative semilunar valve includes a native pulmonary valve, wherein thedownstream artery includes the pulmonary trunk, and wherein positioningthe distal fixation member comprises positioning the distal fixationmember in the pulmonary trunk.
 160. The method according to claim 157,wherein providing comprises coupling the distal fixation member to theproximal fixation member before positioning the distal fixation memberand before positioning the proximal fixation member.
 161. The methodaccording to claim 157, wherein providing comprises coupling the distalfixation member to the proximal fixation member after performing atleast one action selected from the group consisting of: positioning thedistal fixation member, and positioning the proximal fixation member.162. The method according to claim 157, wherein the distal fixationmember and the proximal fixation member are fabricated as one integratedstructure, and wherein providing the distal fixation member coupled tothe proximal fixation member comprises providing the distal fixationmember and the proximal fixation member that are fabricated as oneintegrated structure.
 163. The method according to claim 157, whereinpositioning the distal and proximal fixation members comprisespositioning the distal fixation member in the downstream artery beforepositioning the proximal fixation member at least partially on theventricular side of the native semilunar valve.
 164. The methodaccording to claim 157, wherein the prosthesis includes a prostheticvalve, and wherein positioning the distal fixation member comprisespositioning the distal fixation member such that the valve assumes aclosed position during diastole and an open position during systole.165. The method according to claim 157, wherein positioning the distalfixation member comprises positioning the distal fixation member suchthat it limits an extent of opening of leaflets of the native valvecomplex.
 166. The method according to claim 157, wherein positioning theproximal and distal fixation members comprises: collapsing the proximaland distal fixation members; inserting the proximal and distal fixationmembers, while collapsed, in the ventricle and the downstream artery,respectively; and expanding the proximal and distal fixation members inthe ventricle and the downstream artery, respectively.
 167. The methodaccording to claim 166, wherein positioning the distal fixation membercomprises positioning the distal fixation member in the downstreamartery while collapsed, and expanding the distal fixation member beforepositioning the proximal fixation member at least partially on theventricular side of the native semilunar valve.
 168. The methodaccording to claim 166, wherein inserting the proximal and distalfixation members comprises storing the proximal and distal fixationmembers while collapsed in at least one tube selected from the groupconsisting of: an overtube and a trocar, and wherein expanding theproximal and distal fixation members comprises deploying the proximaland distal fixation members from the selected tube.
 169. The methodaccording to claim 168, wherein the native semilunar valve includes anative aortic valve, wherein the downstream artery includes theascending aorta, and wherein inserting the proximal and distal fixationmembers comprises inserting the selected tube through an apex of a heartof the subject, and advancing the selected tube through the ventricleuntil a distal end of the selected tube passes the native semilunarvalve.
 170. The method according to claim 168, wherein the nativesemilunar valve includes a native aortic valve, wherein the downstreamartery includes the ascending aorta, and wherein inserting the proximaland distal fixation members comprises inserting the selected tube usinga transaortic approach.
 171. The method according to claim 168, whereinthe native semilunar valve includes a native pulmonary valve, whereinthe downstream artery includes the pulmonary trunk, wherein theventricle includes a right ventricle, and wherein inserting the proximaland distal fixation members comprises inserting the selected tubethrough a free wall of the right ventricle, and advancing the selectedtube through the right ventricle past a right ventricular outflow tractof the heart until a distal end of the selected tube passes the nativepulmonary valve.
 172. The method according to claim 157, wherein theproximal fixation member includes an inner support structure, whereinthe distal fixation member includes an outer support structure that isplaced partially over the inner support structure, and whereinpositioning the proximal and distal fixation members comprisespositioning the inner and outer support structures, respectively. 173.The method according to claim 172, wherein the outer support structureis shaped so as to define a plurality of distal diverging strutsupports, from which a plurality of proximal engagement arms extendradially outward, and wherein positioning the outer support structurecomprises rotationally aligning the engagement arms with respective onesof the semilunar sinuses.
 174. The method according to claim 173,wherein positioning the outer support structure comprises rotationallyaligning the strut supports with respective commissures of the nativevalve complex.
 175. The method according to claim 173, wherein aligningthe engagement arms and the strut supports comprises moving the outersupport structure in a proximal direction, such that the engagement armsself-align with the respective ones of the semilunar sinuses.
 176. Amethod for implanting a valve prosthesis at a native semilunar valve ofa native valve complex of a subject, the method comprising: providing adistal fixation member of the valve prosthesis coupled to a proximalfixation member of the valve prosthesis; positioning the distal fixationmember in a downstream artery of the subject selected from the groupconsisting of: an ascending aorta, and a pulmonary trunk, such that thedistal fixation member applies, to native commissures of the nativesemilunar valve, a first axial force directed toward a ventricle of thesubject, without applying any force to native leaflets of the nativesemilunar valve; causing the distal fixation member to rotationallyalign with the native semilunar valve by gently rotating the valveprosthesis; and positioning the proximal fixation member at leastpartially on a ventricular side of the native valve complex, such thatthe proximal fixation member applies a second axial force directedtoward the downstream artery, such that application of the first andsecond forces couples the prosthesis to the native valve complex byaxially sandwiching the native valve complex from a downstream side andthe ventricular side thereof.
 177. The method according to claim 176,wherein the native semilunar valve includes a native aortic valve,wherein the downstream artery includes the ascending aorta, and whereinpositioning the distal fixation member comprises positioning the distalfixation member in the ascending aorta.
 178. The method according toclaim 176, wherein the native semilunar valve includes a nativepulmonary valve, wherein the downstream artery includes the pulmonarytrunk, and wherein positioning the distal fixation member comprisespositioning the distal fixation member in the pulmonary trunk.
 179. Themethod according to claim 176, wherein causing the distal fixationmember to align comprises causing the distal fixation member torotationally self-align with the native semilunar valve.
 180. The methodaccording to claim 176, wherein providing comprises coupling the distalfixation member to the proximal fixation member before positioning thedistal fixation member and before positioning the proximal fixationmember.
 181. The method according to claim 176, wherein providingcomprises coupling the distal fixation member to the proximal fixationmember after performing at least one action selected from the groupconsisting of: positioning the distal fixation member, and positioningthe proximal fixation member.
 182. The method according to claim 176,wherein the distal fixation member and the proximal fixation member arefabricated as one integrated structure, and wherein providing the distalfixation member coupled to the proximal fixation member comprisesproviding the distal fixation member and the proximal fixation memberthat are fabricated as one integrated structure.
 183. A method forimplanting a valve prosthesis at a native semilunar valve of a nativevalve complex of a subject, the method comprising: providing a distalfixation member of the valve prosthesis coupled to a proximal fixationmember of the valve prosthesis; positioning the distal fixation memberin a downstream artery of the subject selected from the group consistingof an ascending aorta, and a pulmonary trunk, such that the distalfixation member applies a first axial force directed toward a ventricleof the subject; and positioning the proximal fixation member at leastpartially on a ventricular side of the native valve complex, such thatthe proximal fixation member applies a second axial force directedtoward the downstream artery, such that application of the first andsecond forces couples the prosthesis to the native valve complex byaxially sandwiching the native valve complex from a downstream side andthe ventricular side thereof, and the prosthesis applies a radial forceof less than 0.5 pounds outwardly against the native semilunar valve.184. The method according to claim 183, wherein the native semilunarvalve includes a native aortic valve, wherein the downstream arteryincludes the ascending aorta, and wherein positioning the distalfixation member comprises positioning the distal fixation member in theascending aorta.
 185. The method according to claim 183, wherein thenative semilunar valve includes a native pulmonary valve, wherein thedownstream artery includes the pulmonary trunk, and wherein positioningthe distal fixation member comprises positioning the distal fixationmember in the pulmonary trunk.
 186. The method according to claim 183,wherein providing comprises coupling the distal fixation member to theproximal fixation member before positioning the distal fixation memberand before positioning the proximal fixation member.
 187. The methodaccording to claim 183, wherein providing comprises coupling the distalfixation member to the proximal fixation member after performing atleast one action selected from the group consisting of: positioning thedistal fixation member, and positioning the proximal fixation member.188. The method according to claim 183, wherein the distal fixationmember and the proximal fixation member are fabricated as one integratedstructure, and wherein providing the distal fixation member coupled tothe proximal fixation member comprises providing the distal fixationmember and the proximal fixation member that are fabricated as oneintegrated structure.